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CHAMBERS'S 



INFORMATION FOR THE PEOPLE 






CHAMBERS'S 



INFORMATION FOR THE PEOPLE 



EDITED BY 



WILLIAM AND ROBERT CHAMBERS 



FIFTH EDITION 



VOLUME L 




W. & R. CHAMBERS 

LONDON AND EDINBURGH 
1834 



Edinburgh : 
Printed by W. & R. Chambers. 



% 



m 




JX- 



PREFACE. 



It is now many years since Chambers's Information for the People first issued from the 
press. The cheapness of the work, its novelty, and the varied mass of useful knowledge 
which was embraced, rendered it a popular favourite. Without adventitious aid, its sale 
was immense. Since that time it has undergone numerous improvements both as regards 
matter and general appearance. Again, from the constant and rapid advance in every branch 
of science and art, it has been deemed necessary to recast the work in adaptation to the 
existing state of human knowledge. Hence the present, or Fifth Edition, which has been 
revised under the able Editorship of Andrew Findlater, LL.D. 

Designed in an especial manner for the People, though adapted for all classes, the work 
will be found to comprise those subjects on which information is of the most importance ; 
such as the more interesting branches of science — physical, mathematical, and moral ; natural 
history, political history, geography, and literature ; together with a few miscellaneous paper.-:, 
which seem to be called for by peculiar circumstances affecting the British people. Thus 
everything is given that is requisite for a generally well informed man in the less highly 
educated portions of society, and nothing omitted appertaining to intellectual cultivation, 
excepting subjects of professional or local interest. It will be understood, then, that the 
Information for the People is not an encyclopaedia, in the comprehensive meaning of 
the word, but rather one embracing only the more important departments of general know- 
ledge. The ruling object, indeed, has been to afford the means oi self-education, and to intro- 
duce into the mind, thus liberated and expanded, a craving after still further advancement 

It may well be said of the present edition, as was said of the last, that the improvements 
are very considerable. The scientific treatises have, in general, been carefully remodelled, 
with due attention to recent discoveries. Subjects the interest of which is past have been 
omitted or greatly condensed, and others of a more enduring and important nature have 
taken their place. In the Indexes will be found a reference to almost every subject 
necessary in ordinary circumstances to be known. 

In one important respect — that of the pictorial illustrations and embellishments — it must 
be obvious, to the most cursory observation, that a very great improvement has been effected. 

W. & R. C 



Digitized by the Internet Archive 

in 2007 with funding from 

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http://www.archive.org/details/chamberssinforma01chamuoft 



CONTENTS. 



Ka Page. 
ASTRONOMY I I 

GEOLOGY 2 17 

METEOROLOGY 3 33 

PHYSICAL GEOGRAPHY 4 49 

VEGETABLE PHYSIOLOGY 5 65 

SYSTEMATIC BOTANY 6, ^ 81 

HUMAN PHYSIOLOGY 8 II3 

ZOOLOGY 9-12 129 

NATURAL PHILOSOPHY— MATTER, MOTION, AND HEAT 13 193 

MECHANICS— MACHINERY I4 209 

HYDROSTATICS— HYPRODYNAMICS — PNEUMATICS I5 225 

LIGHT AND SOUND 16 241 

MAGNETISM AND ELECTRICITY I7, 18 257 

CHRONOLOGY— HOROLOGY 19 289 

CHEMISTRY 20, 21 305 

CHEMISTRY APPLIED TO THE ARTS 22 337 

FICTILE MANUFACTURES 23 353 

TEXTILE MANUFACTURES 24 369 

USEFUL MINERALS 25 385 

METALS — METALLURGY 26 40I 

THE STEAM-ENGINE 27 417 

INLAND CONVEYANCE 28 433 

MARITIME CONVEYANCE 29 449 

ARCHITECTURE 30 465 

WARMING — VENTILATION — LIGHTING 31 481 

SUPPLY OF WATER — DRAINAGE — BATHS 32 497 

AGRICULTURE— CULTURE OF WASTE LAND — SPADE-HUSBANDRY 33,34 513 

THE KITCHEN-GARDEN 35 545 

THE FLOWER-GARDEN 36 561 

THE FRUIT-GARDEN 37 577 

ARBORICULTURE 38 593 

THE HORSE 39 609 

CATTLE — DAIRY HUSBANDRY 40 625 

THE SHEEP— GOAT— ALPACA 4I 641 

PIGS — RABBITS — POULTRY— CAGE-BIRDS 42 657 

THE HONEY-BEE 43 673 

THE DOG — FIELD-SPORTS — ANGLING 44 689 

FISHERIES .' 45 705 

PRESERVATION OF HEALTH 46 721 

FOOD— BEVERAGES , 47 737 

PREPARATION OF FOOD — COOKERY ..48 753 

MEDICINE— SURGERY 49 769 

CLOTHING — COSTUME SO 785 

JNDEX, TITLES, &C ,.....,» , 5If 52 80I 



n 







ASTRONOMY. 



ASTRONOMY teaches whatever is known of 
the heavenly bodies. The earth itself it 
regards only as one of them — viewing it as an 
entire body, such as it would appear were we to 
behold it from a sufficient distance. 

The subject falls naturally under two general 
heads: u/, A description of the heavenly bodies 
— the aspect of the heavens as a whole ; the 
distances, shapes, and magnitudes of the several 
bodies ; the figures they describe in their motions ; 
the way in which they are grouped into systems, 
&c. id, Physical Astronomy, or the nature of 
the powers or forces that carry on the heavenly 
motions, and the laws that they observe. The 
processes of calculating the motions from a know- 
ledge of the laws, with a view to turn them to the 
use of man, and the management of mathematical 
instruments for taking the necessary observations, 
form the art of the practical astronomer; into 
which we cannot enter. 



GENERAL APPEARANCES OF THE HEAVENS. 

When we raise our view to the sky over our 
heads, we find it occupied with the sun by day, 
and the moon and stars by night The sun is 
evidently never at rest, but is either ascending 
upwards in the sky from the east, or else sinking 
towards the horizon or sky-line in the west, where 
his body goes out of sight. The same continual 
motion of rising and setting is observed in the 
moon and in the stars. If, at the beginning of a 
winter-night, we fix our attention on a conspicuous 
star near the east point of the horizon, and con- 
tinue to observe it, we shall see it rising higher and 
higher for about six hours ; it will then begin to 
descend to the west, and in about six hours more 
it will reach the west point of the horizon, and 
disappear. If we commence our watch again on 
the following night, we may discover the same 
star rising at the east point at about the same 
1. 



hour, and going through its course of mounting, 
crossing, and descending the sky as before. 

If we turn to some point between east and north, 
and notice a star just rising, we find it gradually 
ascending in the heavens up to a certain point; 
then descending to the west, and going out of 
sight ; and finally reappearing in the east in about 
twenty-four hours from the time of its previous 
rising: but these twenty-four hours, instead of 
being spent one half above and the other half 
below the horizon, as in the former case, will be 
unequally divided between the presence and the 
absence of the star ; more than twelve hours will 
be taken to pass from the rising to the setting, 
and less than twelve hours will elapse between the 
setting and the next rising. The further north the 
point of rising, the longer the time spent in the 
upper course, and the shorter the time in the under 
and unseen course. If we go to the north point 
itself, and observe a star just a little above the 
horizon, we shall find that it will spend the first 
twelve hours in ascending to its highest point in 
the heavens, and the next twelve in descending to 
the neighbourhood of the horizon ; and it will not 
go beneath at all, but commence again to rise and 
describe a circle in the heavens as before ; such a 
star, therefore, will be always in sight. In like 
manner, all stars in the north quarter lying with- 
in the circle described by this never-setting star 
will perform their daily movement above the 
horizon.* 

Poles, Axis. — In the inside of these circling 
motions we may observe a point in the sky which 

• In the foregoing and in succeeding paragraphs, it is supposed 
that the stars may be seen day and night By the naked eye no 
star can be seen while the sun is up, but they are all in their places 
nevertheless. The intense light of the sun generally makes other 
celestial objects invisible. With g[Ood telescopes, however, the 
stars may lie seen in the daytime, m a clear day, except in the 
sun's immediate neighbourhood. From the bottom oi deep well* 
and mines the stars in the sky overhead are seen through the day. 
When the moon is at a considerable distance from the sun, it may 
be seen when the sun is up. 

I 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



seems to be their common centre. A star lying 
in it would be perfectly at rest, and stars near it 
describe very small circles, or move within narrow 
limits. This point of rest is situated in the north 
quarter of the heavens, more than half-way up 
from the sky-line, towards the summit. It is called 
the north celestial pole, or the north pole of the 
heavens, and is the most important point in the 
sky for astronomical references. No visible star 
is actually residing in it ; but a very bright star 
lies near it, called for that reason the pole-star. 

By observing the movements of stars that rise 
in the south-east, and seeing their visible paths 
becoming shorter and shorter, as they lie more 
southward, we cannot help inferring that there is 
a large region of stars describing circles wholly 
out of sight, and that there is a point beneath, 
which is the centre of these circles, corresponding 
to the centre of the northern heavens. This point 
is called the south celestial pole. An imaginary 
line drawn from pole to pole, or from the elevated 
north resting-point to the concealed south resting- 
point, is called the axis of the heavens, or the axis 
of the world. Owing to one pole being a con- 
siderable way up in the sky, and the other far 
down out of sight, it is evident that the great 
whirl of the starry sphere goes on in a slanting 
direction. 

Besides the poles and axis of the heavens, there 
are many other imaginary points, lines, and circles. 



terminating in the north and south celestial poles, 
EQ the celestial equator, NS the horizon, and N 
and S the north and south points of it, Z the zenith, 
and D the nadir ; then the enclosing circle of the 
figure NPZES/DQ is the meridian. 

It is evident from this description, that when^ 
the sun or the moon passes the meridian, or lies 
due south, it has reached its greatest height, and 
will immediately commence to descend. Hence, 
also, we can determine the meridian line in the 
heavens, by observing where a star is when it 
ceases to ascend and begins to descend ; which 
of course gives us the direction of the north and 
south points, and serves the same end as the 
mariner's compass. It is evident, also, that the 
middle point between a body's rising and setting 
is its meridian passage. 

Fixed Stars and Wanderers. — Although the 
general starry sphere turns round in one great 
mass, so that each star is always in the same 
place among the other stars, it was early observed 
that there were exceptions to the common move- 
ment ; and that a small number, besides going 
round the sky daily, shift about among the others. 
In opposition to these erratic or wandering 
bodies, the general multitude that kept their places 
were c^XSe^L fixed stars. 

The moon, for example, is soon observed to be 
an erratic body. One night we see it near one 
star, and the next night it is at a considerable 



which it is convenient to suppose drawn among I distance to the east of it ; even in a few hours 



the stars, and which of course we can actually 
draw in all figures and sketches of the starry 
heavens. The most important of these may be 
here explained. 

Equator, Horizon, Zenith, Meridian. — The ce- 
lestial equator, so called because it cuts the starry 
sphere into two equal halves, is an imaginary 
circle passing round the heavens midway between 
the two poles. The two halves into which it divides 
the sphere of stars form the northern and southern 
hemispheres. 

The horizon, or the line where the earth seems 
to meet the sky, makes another division of the 
starry sphere, into the visible hemisphere, or stars 
above the horizon; and the invisible, or stars below 
the horizon. The point of the heavens directly 
over our heads, or the very summit of our sky, is 
called the zenith. The point that we should see 
directly beneath our feet, if the earth could be 
seen through, is called the nadir. 

Another artificial circle supposed to be drawn 
in the heavens, is the meridian. Like the equator 
and the horizon, it divides the starry sphere into 
two equal half-spheres, but in a different direction 
from either of those circles. In fact, it is so drawn 
as to be perpendicular 
to both. It passes 
through the north point 
of the horizon, then up- 
ward through the north 
celestial pole, through 
the zenith, down through 
the south point of the 
horizon, through the 
south celestial pole 
beneath, and finally 
through the nadir : so 
that, in the first place, it lies north and south ; 
and in the second place, it stands upright. Thus, 
if in the figure, '9p be the great axis of the heavens 




there is a visible change of position. In the course 
of a month, we find it has gone through a complete 
circle from west to east among the stars, and come 
back nearly to the same place. 

The sun has a similar motion, though it is 
slower, and also less easily marked, because his 
light prevents the stars from being seen at the 
same time. If we could see a star any night 
setting at the same instant as the sun, we should 
find that the next night it would set four minutes 
before the sun, the sun having in the meantime 
moved backward a short distance. 

Ecliptic, Latitude, Longitude, Declination, &c. 
— When this motion of the sun among the stars 
is observed for a length of time, it is found that it 
forms a circuit, bringing him back, in the course 
of a year, to the same position. The path, how- 
ever, which he travels, is not exactly east and west, 
or parallel to the equator. If this were the case, 
the sun would rise and set always in the same 
points of the horizon. But we see that on the 
2 1st of March, for instance, he rises exactly in the 
east ; for the next three months the point of his 
rising is more and more north of east, till the 
2 1st of June, when it begins to recede, and again 
reaches the east point on the 21st of September ; 
and during the winter months it makes a similar 
approach to and retreat from the south. The 
amount of divergence either way is about a fourth 
of the distance between the east point and the 
north or south point. From this, and other appear- 
ances, it is evident that the annual path described 
by the sun among the stars runs slanting across 
the equator. This is an important circle in astro- 
nomy, and is called the Ecliptic; the angle which 
it makes with the equator is called its obliquity, 
and on this depends the variety of the seasons. 
Its amount is about a fourth of a quarter circle 
(23° 28'). 

The points where the celestial equator and the 



ASTRONOMY. 



ecliptic cross one another are called the equinoctial 
points, because the sun is in them at the equinoxes. 
The vernal equinoctial point, called Aries, is used 
as a fixed mark from which to measure distances 
on the heavens east and west, just as we measure 
distances east and west on the earth, or terrestrial 
longitude, from Greenwich. 

The terms latitude and longitude have different 
meanings in astronomy and in geography. The 
latitude of a place on the earth's surface is its 
distance north or south of the equator ; the lati- 
tude of a planet or star is its distance from the 
ecliptic, while its distance from the celestial equator 
is called declination. The longitude of a place 
is its distance east or west from the first meridian 
counted along the earth's equator ; longitude in 
the heavens is distance eastward from the point 
Aries, measured in the direction of the ecliptic, 
and not in that of the equator. The distance of 
a heavenly body from Aries, measured in the direc- 
tion of the celestial equator, is called its right 
ascension. The reason why the ecliptic is chosen 
to refer the latitudes and longitudes of the heavenly 
bodies to, is, that it is the only circle m the 
heavens that approaches to the permanency of the 
earth's equator ; it maintains almost a fixed posi- 
tion among the stars, while the celestial equator 
shifts its position in the course of ages, and thus 
divides the starry sphere differently at different 
periods. 

Besides the sun and moon, there are a good 
many other wandering stars. The ancients dis- 
covered five of these, and gave them the name of 
planets, from the Greek word ' to wander.' The 
rest have been discovered since the invention of 
the telescope. 

Copernican and Ptolemaic Systems.— vlt nave 
hitherto spoken of the appearances of the heavenly 
bodies and their motions, without inquiring 
whether they are as they seem. These appa- 
rent motions were long considered to be real 
motions. The earth was believed to be— what it 
■seems to be— a fixed station, the centre of the 
universe; the starry sphere was a solid shell, 
revolving daily with its thousand fixed fires round 
the central earth ; while within it were a succes- 
sion of crystal spheres, carrying the sun, moon, 
and planets, and, while partaking of the common 
■motion from east to west, having also each a 
motion of its own. But as observations of the 
planetary motions were multipHed, it became 
more and more difficult to account for all the 
appearances in this way. At last it was found 
necessary altogether to change the point of view 
—to give up the earth as the centre of all the 
heavenly motions, and admit that it itself, along 
with the other planets, is in motion round the sun 
as a centre. This view, called the Copernican 
system, from Copernicus, its author, or rather 
reviver— for it had been held by more than one 
ancient philosopher— is now universally prevalent ; 
the earlier is known as the Ptolemaic system, from 
Ptolemy, the chief ancient writer on the subject 
whose works we possess. 

Instead of attempting to state the arguments 
by which the old opinions are refuted, we will 
proceed at once to give an outline of what is now 
believed to be the arrangement and constitution 
of the heavenly bodies. The simple way in which 
the Copernican system accounts for all the appear- 
ances, is the best argument in its favour. 



THE SOLAR SYSTEM. 

Of the heavenly bodies, those spoken of above 
as wanderers compose a group altogether apart, 
the earth being one of them. The sun, which is 
vastly greater than all the rest put together, forms 
the centre of the group ; which is hence called the 
solar system (from sol, the Latin word for * sun '). 
Though the distances of the bodies of this group, 
from the central sun and from one another, are 
enormous when measured by ordinary terrestrial 
standards, they become as nothing when compared 
with the space that separates the whole of them 
from the nearest of the fixed stars. The solar 
system forms thus a compact inner world, cut off 
by an almost immeasurable chasm from the outer 
universe. It is with this inner world that the 
astronomer has chiefly to do ; what is known of 
the fixed stars will be spoken of apart, under the 
head of Sidereal Astronomy. 

Around the sun as a centre, the smaller bodies 
or planets wheel at different distances in paths or 
orbits of a round form, being what are called 
ellipses ; these orbits lie pretty nearly in the same 
plane, a plane passing through the sun's centre ; 
and the motions of the planets are, as a general 
rule, all in one direction — from west to east. 

Some of the planets have other planets moving 
round them as centres— the moon, for instance, 
round the earth. These are called secondary 
planets, moons, or satellites; while those that 
move round the sun are called primary planets. 
The primary planets now known consist — ist, of 
eight larger planets, including the Earth ; their 
names, in the order of their nearness to the sun, 
are— Mercury, Venus, the Earth, Mars, Jupiter, 
Saturn, Herschel or Uranus, and Neptune. 2d, 
A group of small planets, called sometimes also 
asteroids, of which more than two hundred are 
now known. They are situated between Mars 
and Jupiter. 

The sateUites or moons, as yet discovered, 
number eighteen ; of which the Earth has one, 
Mars two, Jupiter four, Saturn eight, Uranus four, 
and Neptune one. In addition to its moons. 
Saturn is attended by a luminous ring. 

Those singular bodies called comets (Lat. coma, 
a lock or brush of hair) also belong, many of them 
at least, to the solar system. And in addition to 
the above luminous members of the system, it is 
now becoming apparent that there are multitudes 
of dark bodies, of various sizes, circling »n the 
spaces between the known planets, some of which 
become visible to us when they accidentally enter 
our atmosphere as shooting-stars and other forms 
oi meteors. See METEOROLOGY. 

Such is a brief inventory, as it were, of the 
furniture of this inner world to which we belong. 
The figure on the following page represents the 
relative positions of the chief planetary orbits. 
Appended are tables of the diameters, distance, and 
other numerical particulars of the several bodies. 

Astronomical Mensuration.— Though, it would 
be inconsistent with the scope of the present 
sketch to describe minutely the processes by whicb 
these numbers are found, it is necessary to g^ve 
a general idea of the methods followed, that the 
reader may be able to conceive the possibility of 
measuring and weighing objects so completely 
beyond our reach. ^ 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



I 




The Solar System, to the orbit of Neptune. 





Diameter in 
MUes. 


Density, 

Earth's 

being = I. 


Mass, Sun's 
being = i. 


Distance from 

Sun in 

Millions of 

Miles. 


Period of 

Revolution 

in Days. 


Velocity in 

Orbit— Miles 

per Hour. 


Velocity of 
Rotation at 
Equator — 
Miles per 
Hour. 


Mercury 


2,962 

7,5 «o 

7,912 
4,920 

88,390 
71.904 
33,024 
36,620 
852,584 


124 
0.92 
100 
0.52 

0-22 
0-I2 
018 
0.17 

o-2<; 


« 8 e s 7 K 1 


92i 
139 

476 
872 

1 754 
2746 


88 

225 

4.332 

10,759 
30,687 

60,127 

« 

♦ 


105,330 
77,050 
65.533 
53.090 

28,744 
21,221 
14,963 

11,958 

* 

2,273 


386 
1,010 
1,040 

628 

27,985 

21,538 

10,921 

» 

4,407 
10 


Ve.vus... 

Earth. 


» 1 i 7 e 
me 

S48«V 

lB78t 

I 


M\RS 


Minor Pianets. 
Jupiter 


Saturn 


Uranus 


Neptune 


Sun 


MiX)N 


2,153 1 o-6^ 


1 1 • 










' 





The astronomer finds the distance between 
objects, not by measuring lines, but by measuring 
angles. Even distances on the earUi are most 
A ^. E 




accurately measured in this way, as in trigono- 
metrical surveying. Suppose that an obser\'^er at 
A wishes to ascertain the distance of an inacces- 
sible object at B ; it could never be found by 
looking at it from A alone. He chooses another 
station, C, to which he has access, in a direction 
perpendicular, we shall say, to the direction of B, 
and at a convenient distance, say 100 yards. If 
the object looked at from A lay directly east, it 
will no longer be east when looked at from C ; its 
direction is now CB, not CE, and the difference 
of direction is seen in the greater or less wideness 
4 



of the opening between those two lines, or in the- 
angle BCE, as it is called. The size of such an 
angle is ascertained by describing a circle from the 
point C, and measuring how many degrees (that 
is, 360th parts of the circle) the arc dc contains. 

By considering the figure, it will be seen that 
the more distant B is, the smaller must be the angle 
BCE, and also ABC, which is evidently equal to 
BCE. For every size of the angle ABC, there is 
a certain fixed length of AB (the length of AC 
remaining the same) j and trigonometry teaches,, 
from knowing the base AC and the angle opposite,, 
to find the length of AB. Everj'thing depends on 
measuring the angles of (direction, or the angular 
distances, accurately. Degrees are divided each 
into 60 parts, called minutes, and these again into- 
60 parts, called seconds; and astronomical instru- 
ments are now so delicate that a difference of 
direction of one second can be measured. 

The difference of direction in which a body 
is seen when viewed from two places at a dis- 
tance from one another, is called by astronomers. 



ASTRONOMY. 




jfiarallax, or displacement. The annexed figure re- 
presents the effect 

* of parallax on a 
heavenly body C. 

* V is its true place, 

or place in the 
sky as seen from 
the earth's centre ; 
T is its place as 
seen from the sur- 
face at A, and the 
arc TV, or the 
angle ACE, is the 
amount of the 

* horizontal paral- 
lax. 

The distances of the heavenly bodies, even the 
nearest of them, are so great, that even when the 
two stations are taken as wide apart as possible — 
that is, from the opposite sides of the earth, where 
the distance between them is equal to the earth's 
•diameter, or nearly 8000 miles — the angle of paral- 
lax ACB, or the displacement on the sky TS, is 
very small. In the case of the moon, the nearest 
of the heavenly bodies, it is nearly two degrees ; 
and by means of it the distance of the moon is 
found to be about 239,000 miles, or about sixty 
times the half-diameter or radius of the earth. 
When the sun is observed from opposite sides 
of the earth, he suffers a displacement of only 
seventeen seconds of a degree. On so small an 
angle, a slight error of observation materially 
affects the result ; and therefore other expedients 
were had recourse to, to determine the sun's dis- 
tance with greater certainty and exactness, which 
may be stated in round numbers as 92,500,000 
jTiiles. When the distance of the earth from the 
sun was once known, a new and vastly extended 
base was obtained for the trigonometrical survey 
of the heavens. As the earth travels in its annual 
circuit round the sun at the distance of 92,500,000 
miles, by observing a heavenly body at two differ- 
ent times, at an interval of six months, we in effect 
observe it from two stations removed from each 
other by the whole breadth of the earth's orbit, 
or nearly 185,000,000 miles. The displacement 
produced in this way is called annual parallax. 
Even this enormous base becomes as nothing 
when applied to measure the distances of the fixed 
stars ; by far the greater number shewing no 
■sensible parallax. 

Knowing the distances, we can find the real 
sizes of bodies from their apparent size, or from 
their dimensions, taken by an angular instrument. 
If an object be a mile off, and if its breadth make 
an angle of 1° at that distance, its lineal breadth 
is determined by these two quantities. Thus the 
moon, being about 239,000 miles from the earth, 
and having an angular breadth in the sky of 
somewhat more than half a degree, its actual 
breadth must be about 2000 miles. The accurate 
estimate is 2153 miles. The sun has almost 
the same apparent size in the sky as the moon ; 
but being at nearly 400 times the distance of the 
moon, it must have nearly 400 times the breadth 
of the moon to appear equaily large. The diam- 
eters of the planets are determined in the same 
way. 

The solid contents or volumes of the several 
bodies are found from their diameters, by a simple 
rule of geometry. To state the numlier of cubic 



I miles that each contains, gives little real infor- 

! mation, the important thing being their relative 

I magnitudes. Now, it is important to bear in 

rnind that the magnitudes or bulks are not in the 

[simple proportion of the diameters, but as the 

cubes of the diameters. Thus, the diameter of the 

sun being about 107 times that of the earth, his 

volume or bulk will be 1,200,000 (107 cubed) times 

greater. 

To speak of weighing such stupendous masses 
as the sun, moon, and stars, seems at first sight 
extravagant ; yet it is by no means one of the 
most difficult problems, as will be explained under 
Physical Astronomy. 

Diameter of the Earth. — In measuring the dis- 
tances of the heavenly bodies, the diameter of 
the earth is taken as a known base to start from ; 
but how is this got at? If at any place we 
observe the height of a star on the meridian — say 
the pole-star — and after travelling directly north 
for a considerable distance, observe the height of 
the same star, it will be found to be greater. 
This arises from the round form of the earth ; and 
it is easily shewn that, if the star has risen one 
degree higher in the heavens, the observer must 
have moved north one degree. We are thus 
enabled to fix two stations on a meridian, the dis- 
tance between which shall be exactly one degree, 
or the ^"BTjth part of the whole circle or circum- 
ference of the earth. When the length of such a 
line is measured, it is found to be a little less than 
seventy English miles. This, multiplied by 360, 
gives the whole circumference in round numbers 
at 25,000 miles, and the diameter at 8000. 



SEPARATE MEMBERS OF THE SYSTEM. 

The Sun (-0). — The apparent or angular breadth 
of the sun, at the mean distance of the earth, is 
slightly more than 32'. The real diameter of the 
sun is 853,380 miles, which, as already stated, is 
107 times that of the earth, so that in volume or 
bulk the sun is equal to 1,200,000 earths. 

That the sun is a ball or globe is evident from 
its always appearing round, while we know, at the 
same time, that it turns or rotates on an axis. 
The fact of its rotation, and the time it occupies, 
are inferred from observing the motion of the dark 
spots which are seen at times on its surface : the 
period of rotation is ascertained to be a little over 
25 days. 

A solar spot presents the appearance of a black 
irregular patch, called the umbra, surrounded by 
a less dark fringe, called the penumbra. Spots 
appear and disappear very irregularly, some lasting 
only a day, others for weeks and even months. 
Sometimes few or no spots are to be seen, at other 
times they appear in profusion ; and these alter- 
nations are observed to come regularly round in 
periods of about ten years. Individual spots have 
been seen to attain the enormous breadth of 
50,000 miles, covering an area of five times the 
surface of the earth. They are inferred, with 
almost certainty, to be hollows. 

Around the spots, and on other places, there 
are often masses brighter than the general surface, 
which are called yd!f«/«, or torches. The general 
surface itself is not uniform, but appears to be 
coarsely mottled, and to be made up of bright 
roundish patches, with soft edges, sprinkled irregu- 
larly on a less luminous background. The move- 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



ments and changes, of almost incredible velocity 
and magnitude, constantly going on in the spots 
and bright patches lead irresistibly to the conclu- 
sion that the luminous surface of the sun— his 
fihotosphere, as it is termed— is of a cloudy nature. 
But during a total eclipse of the sun, when his 
shining disk is covered by the dark body of the 
moon, there is readily seen a white halo called 
the corona, surrounding the moon ; within this 
there were first observed fantastically shaped 
masses of a red colour, projecting considerably 
here and there beyond the moons edge, ana 
variously called red flames and red prominences ; 
and closer obser^-ation has shewn that these larger 
prominences are connected by a continuous belt 
of similar colour at a lower level. This less 
brilliant envelope is known as the chromosphere. 

By bringing that new and marvellous instru- 
ment of investigation, the spectroscope, to bear on 
those appearances, a good many points have oi 
late been established regarding the physical con- 
stitution of the sun— that is, what substances it is 
composed of, and the condition in which those 
substances exist. To explain the action of the 
spectroscope belongs to Optics ; it is sufficient 
here to say, that it tells whether a distant luminous 
body is in a solid or liquid state, or whether it is 
in the state of vapour; and can discriminate 
between the light proceeding from incandescent 
hydrogen, for instance, and that from the vapour 
of sodium or of iron. The chief results arrived at 
may be thus summed up : The sun is composed 
of substances identical, in part at least, with those 
composing our earth; hydrogen, sodium, iron, 
magnesium, and several other metals have already 
been fairiy ascertained. The matter of the sun is 
so intensely hot as to be to a great extent m the 
state of vapour ; at all events, it is so to a consid- 
erable depth at the surface. The outer envelope, 
or cromosphere of the sun, consists mainly of 
hydrogen. Below this, we have the photosphere, 
or region containing metallic vapours, along, prob- , 
ably, with numerous deposited cloud-particles of , 
these vapours, which particles are the chief source 
of the light and heat of the sun. The photosphere 
is in a state of constant agitation, like that of ! 
boiling, caused, apparently, by the portions on the ] 
surface cooling by radiation and rushing down at 
one place, while hotter matter from the interior i 
is heaved up at another. When these 'convection- | 
currents' are exceptionally violent, they become , 
visible as faculae and spots, the blackness of the 
latter being caused by a great down-rush of the 
comparatively cold matter from above into a 
hollow of the photosphere. This agitation of the 
photosphere causes a corresponding commotion 
in the chromosphere; where the photosphere 
is upheaved, masses of the red-hot hydrogen 
envelope are projected far above the general 
level, sometimes to the height of tens of thou- 
sands of miles, and form prominences. The velo- 
city of these uprushes, and still more of the 
whirling motions going on in the hydrogen, is 
astonishing, being sometimes not less than 120 
miles a second. The nature of the corona is yet 
not fully ascertained. 

As to the sun's heat, it has been calculated 
that the amount given out by one yard of his 
surface is as great as that which would be pro- 
duced by burning six tons of coals on it each 
hour. The amount received by the earth in one 



year would be sufficient to melt a layer of ice 100 
feet thick all over the earth's surface. But the 
sun's heat is given out equally all round, so that 
the portion intercepted by the earth at its distance 
of 92,500,000 miles must be an inconceivably small 
fraction of the whole that is lost by the sun. 

Is the sun becoming cooler with all this loss T 
It must be so, unless the loss is in some way made 
up. The most probable theory of the origin of 
the existing store of solar heat is, that the matter 
composing the sun was originally diffused in a 
nebulous form throughout space, and that this 
matter, falling together by gravity, had its motion 
converted into heat, just as two stones are heated 
by clashing together. But we know of no source 
from which the continual dissipation is replen- 
ished ; and without fresh fuel, the fire, however 
big, must in the end go out. ' There will come a 
time when the sun, with all its planets welded 
into one mass, will roll, a cold black ball, through 
infinite s\i3.ce.''—Lockyer's Astronomy. 

Mercury (5) and Venus ($), the two members of 
the system next to the central body, are called 
inferior planets, from their orbits being within 
that of the earth. Owing to their position, they 
can never appear at any great distance or elonga- 
tion from the sun. Mercury, in fact, even at its 
greatest elongation, sets long before the end of 
twilight, or if west of the sun, does not rise till 
the dawn has begun ; so that in our latitude and 
cloudy climate, it is rarely seen with the naked 
eye. Venus attains more than twice the elonga- 
tion of Mercury, and is seen long after night has 
fairly set in, or before the morning twilight. Both 
inferior planets go through phases like the moon,, 
and when seen through a telescope, have a cres- 
cent or a gibbous shape. They are never seen 
when full, or when new, being then near the sun. 
Venus is the most conspicuous of the heavenly 
bodies, next to the sun and moon ; when it rises- 
before the sun, it is called the Morning Star— 
the Lucifer of the ancients ; and when it sets after 
the sun, it is the Evening Star or Hesperus. 

Telescopic observations of Mercury and Venus 
are very difficult, owing to the intense brilliancy 
of the surface ; hence nothing has been ascer- 
' tained as to their physical constitution. Ever* 
the times of their rotation on their axes cannot be 
i held as accurately determined. 
{ The Earth (®) is the third planet in order from 
' the sun, and closely resembles Venus. The 
' earth is not a perfect sphere ; it does not measure 
the same in all directions, but has its axis, or 
the diameter on which it rotates, shorter than 
its diameter at the equator. This is a general 
law in all planets, the cause of which will be 
explained afterwards. The earth, then, is flat- 
1 tened at the poles, and its shape is called by 
astronomers an oblate spheroid. If it were cut 
in two, by a plane passing through the two poles, 
the section would be, not a circle, but an oval, or 
' ellipse; and the excess of the equatorial diameter 
over the polar diameter is called the ellipttaty of 
the spheroid. The ellipticity of the earth is found 
to be -sirr, or the equatorial diameter exceeds the 
polar by iriirth of its length. This was determined 
in two ways : by measuring degrees . of the meri- 
dian at different latitudes ; and by measuring the 
variation in the force of gravity, between the 
equator and the poles. The polar diameter, omit- 
ting fractions, is 7899 miles, the equatorial 792S ; 



ASTRONOMY. 



the difference is thus 26 miles, and the mean 
diameter 7912 miles. 

To ascertain the density of the earth, is a deli- 
cate problem, to be more particularly described 
under the head of Mechanical Astronomy. It is 
found to be from 5^ to 6 times that of water. 
The densities of the other heavenly bodies are 
always given as compared with that of the earth, 
which is stated as i. The motions of the earth, 
and the appearances caused by them, as well as 
the motions of its accompanying satellite, the 
moon, will be described under separate heads (see 
also Physical Geography). 

Mars (^), the fourth in order, is the nearest to 
us of the superior planets. In many respects it 
resembles our earth. It is distinctly ascertained 
to turn on its axis in 24 hours 37 minutes, the 
axis being inclined to the plane of its orbit at an 
angle of 28° 27'. Its days, then, are nearly the 
same as ours ; and its year, which contains 668 
Martial days, is varied by seasons like the ter- 
restrial year. Mars has a reddish aspect. Around 
each pole is a region of dazzling white, conjec- 
tured to be snow. In 1877 it was discovered to 
be attended by two satellites. 

The asteroids or small planets circulate in a 
region lying between the orbits of Mars and 
Jupiter, but on the whole nearer to the former. 
They form a distinct group of themselves. It is 
only recently that the existence of the small 
planets has become known, the first, Ceres, having 
been discovered in 1801. From observing, how- 
ever, that the distances at which the planets 
generally succeed one another, form a kind of 
progression, that of each orbit, counting from 
Mercury, being nearly double of the one preced- 
ing, it had long been conjectured that a planet or 
planets might yet be discovered in the interval 
between Mars and Jupiter, which formed a break, 
as it were, in the regularity of the progression. 
The discovery of Ceres by Piazzi at Palermo in 
Sicily Qan. i, 1801), was speedily followed by that 
of Pallas, Vesta, and Juno ; and up to the present 
time more than 200 have been catalogued and 
named. 

In addition to their comparative smallness, the 
planets of this group are distinguished by their 
orbits being much more elliptical or elongated 
than those of the others, and also having a greater 
inclination — that is, rising and sinking much 
farther from the plane of the ecliptic. The in- i 
clination of Pallas is as much as 34° 37'. The ! 
diameter of the largest of the minor planets is | 
only 228 miles, and many of the smaller ones ' 
are less than 50. They are invisible to the naked j 
eye, except occasionally Ceres and Vesta. | 

From various observed facts, cosmogonists 
presume that the matter which in other cases has 
gone to form one planet of the first rank, has 
in their case been separated into several parts, 
assuming various but connected orbits. 

Jupiter (2t). — The largest of all the planets is 
Jupiter. The diameter of Jupiter being upwards 
of eleven times that of the earth, his volume is 
1400 times the volume of the earth. To the 
inhabitants of Jupiter the sun must appear less 
than one-fifth of the breadth he presents to us. 
By means of permanent marks, it is ascertained 
that the planet rotates on an axis inclined to 
its orbit at the small angle of 3" 4', and in the 
short space of 9 hours 55 minutes. This makes 



the rotary velocity of Jupiter's surface twenty- 
seven times greater than that of the earth. 
Viewed through, a telescope, Jupiter appears tra- 
versed by dusky streaks parallel to the planet's 
equator. Both Jupiter and Saturn have atmos- 
pheres so densely laden with clouds that the 
surfaces of the planets are, it is believed, never 
seen ; and the parallel streaks, which both ex- 
hibit, are supposed to arise from the rapid rotation 
of those planets disposing the clouds in belts, on 
the principle of our trade-winds and calm-belts. 
The density of Jupiter, taking his bulk as we see 
it, is little more than that of water ; but if he is 
surrounded by a thick envelope of cloudy atmos- 
phere, the kernel of the planet may approach that 
of the earth. The same may be said of Saturn, 
whose density as a whole is about half that of 
water. 

Jupiter is attended by four satellites, which 
revolve round it as the moon revolves round the 
earth, but in much shorter periods— the nearest 
requiring only forty-two hours. One of these 
satellites is of the same size as our moon ; the 
others, larger. Their density is very small ; so 
that the mass of the whole is only a 6ocx)th part 
of that of Jupiter itself. The satellites of Jupiter 
were discovered by Galileo, being among the first 
results of the invention of the telescope. 

Saturn (h) with its ring, or rather rings, and 
eight moons, is the most remarkable member of 
the solar system. It turns on its axis in 10 hours 
29 minutes. 

The ring of Saturn, which surrounds the planet 
in the plane of its equator, is found, on closer 
examination, to consist of a series of rings one 
within the other, the two outer being bright, and 
the innermost dark and transparent. The distance 
from the body of the planet to the dark ring is 
9760 miles. The whole ring system, inclusive of the 
interval between the two bright rings, is 37,570 
miles broad, while its thickness appears not to 
exceed 100 miles. In certain positions of the 
planet, we can see its surface at a considerable 
angle, and the openings or loops which it forms at 
the sides of the planet. At other times, we see its 
dark side, or only its edge. It is now generally 
believed that these rings are composed of innumer- 
able small satellites, moving each in its own orbit 
round the planet, and presenting a bright appear- 
ance where they are densely packed, but a dim 
appearance when scattered. 

The eight satellites of Saturn revolve around it, 
on the exterior of the ring, and almost all of them 
in nearly the same plane. They are so small as 
not to be visible without a powerful telescope. 

Uranus (^) is invisible to the naked eye, and 
was discovered by Sir William Herschel in 1781. 
Owing to its enormous distance, little is known 
regarding it. 

Uranus is attended by at least four satellites. 
In two respects, these satellites are quite singular : 
their orbits are nearly perpendicular to the plane 
of the ecliptic ; and their motions in the orbits are 
retrograde — that is, from east to west, instead of 
being from west to east, like those of all other 
planets both primary and secondary. 

The discovery of Neptune ( ^^ ) is one of the 
greatest triumphs of scientific astronomy. From 
irregularities observed in the motion of the planet 
Uranus, it had been conjectured that some dis- 
turbing cause, not yet discovered, was acting upon 

7 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



it Two astronomers, M. Le Verrier, in Paris, 
and Mr J. C. Adams of Cambridge, independently 
of one another, calculated where this disturbing 
cause must be situated. The results of Le Verrier 
were first made public ; and Dr Galle of Berhn 
detected the new planet at the first search, Sep- 
tember 23, 1846, within two diameters of the 
moon's disk from the place assigned for it by both 
astronomers. 

UNIFORMITIES OR LAWS IN THE SOLAR SYSTEM. 

These details of the movements, magnitudes, 
distances, &c. of the separate members of the 
solar system, are apt at first sight to appear a 
mass of imconnected facts, without any discern- 
ible plan ; but more attentively considered, they 
display in several respects order and law. 

The first important uniformity to be noticed 
among the planets is, that their orbits lie all nearly 
in one plane. If we take the plane of the earth's 
orbit, which is the same as that of the ecliptic, as a 
standard of reference, and suppose it represented 
by a ring held horizontally with the sun in its 
centre, then the other orbits will be represented by 
other rings, two within, and the others without, held 
so as also to have the sun in the centre, and (with 
the exception of a few of the planetoids) never rising 
above or sinking below the level of the earth's ring 
more than a very few degrees. In consequence of 
this arrangement, the motions of the planets, as 
seen from the earth, are confined to a narrow zone 
of the heavens, extending 9° on each side of the 
ecliptic. This circular belt, called the Zodiac^ was 
from the earliest times divided into twelve equal 
parts, called signs, containing, of course, 30° each. 
These signs received each a particular name, from 
the groups of stars or constellations in them having 
a fancied resemblance to certain figures, chiefly 
of animals. The names of the signs, with the 
symbols by which they are usually represented, 
are as follows : 

cp Aries, the Ram. ^ Libra, the Balance. 

Ji Taurus, the Bull. V\^ Scorpio, the Scorpion. 

n Gemini, the Twins, f Sagittarius, the Archer. 

52 Cancer, the Crab. V3 Capricomus, the Goat. 

Ji Leo, the Lion. i^ Aquarius, the Water-bearer. 

n^ Viigo, the Virgin. X Pisces, the Fishes. 

This division of the zodiac affords a ready 
means of pointing out the place of a planet, or of 
the sun or moon, at any particular time, by telling 
in what sign it is. 

Besides moving nearly in one plane, the planets 
move all in one direction — namely, from west to 
east. The same law prevails among the satellites, 
with the remarkable exception of those of Uranus, 
which have a retrograde movement, or from east 
to west 

But the grand uniformities of the solar system 
are those discovered by the celebrated astronomer 
Kepler, and known as ' Kepler's Laws.' Kepler 
merely deduced them as matters of fact from the 
observations of himself and others ; it remained 
for Newton to discover their cause. One of these 
laws respects the exact form of the paths in which 
the planets move. The ancients, from some 
imaginary perfection which they attributed to the 
circle, had taken it for granted that all celestial 
movements must be circular ; Kepler made the 
important discovery that this is an error, and that 
the planetary orbits are ellipses. 




The ellipse is an important figure in astronomy ; 
for not only are the planetary orbits ellipses, but 
the planets themselves have an elliptical shape, as 
we saw when speaking of the form of the earth. 
There is a ready practical way of describing an 
ellipse, which at the same time gives a good 
sensible notion of its nature. If the ends of a 
thread are fastened by 
pins to two points S 
and J, at a distance 
apart less than the 
length of the thread, 
and if the point of a 

{)encil P, is put into the 
oop of the thread, and 
moved round so as to 
keep it stretched, the pencil will trace an ellipse. 
The two points S and s are called the foci of the 
ellipse ; AB is the major or transverse axis, C the 
centre ; and SC, the distance of the focus from the 
centre, is the eccentricity. With the same length 
of thread, a variety of ellipses may be described, 
by altering the distance between the points S 
and s. The nearer they are brought to each other, 
the rounder does the figure become ; and when 
they come together, it forms a perfect circle. In 
the planetary orbits, the sun is always in the focus 
S, and therefore the planet is at different distances 
from the sun in different parts of its orbit. When 
it is at A, the nearest point, it is said to be in 
perihelion; and when at B, in aphelion. SE is the 
mean distance, and is equal to AC. The planetary 
orbits differ very little from circles, or have very 
little eccentricity. 

Another of Kepler's laws connects the change 
of a planet's distance from the sun with the speed 
of its motion : when the distance increases, the 
speed diminishes J and at the least distance we 
find the greatest speed. The exact nature of the 
relation is expressed by saying that the areas 
swept over by the line joining the sun and planet, 
which line is called the Radius Vector, are equal 
in equal times. This is known as the law of 
Equal Areas. 

The two laws already noticed refer to the 
motions of a single planet ; the third law shews a 
relation between the motions of all the planets, or 
all the bodies that revolve round the same centre- 
It is, that the squares of the periodic times of any 
two planets are to each other as the cubes of their 
mean distances from the sunj that is, if there be 
two planets, and one farther off than the other, 
the near planet will perform its revolution quicker 
than the other, in the proportion above expressed. 
The same three laws apply to the revolutions of 
satellites about their primaries. 

DIURNAL AND ANNUAL MOTIONS OF THE EARTH. 

The earth, like all the other planets, has two 
motions : it whirls round its axis once a day ; and 
while doing so, it is all the while travelling bodily 
through space in a wide circuit round the sun, 
which it accomplishes in a year. The first is 
called a motion of rotation, the second of transla- 
tion. The two combined give rise to the vicissi- 
tudes of day and night, and of the seasons. 

The circumference of the earth being 25,000 
miles, any spot at the equator, in order to go 
round in twenty-four hours, must move upwards 
of 1000 miles an hour. This velocity decreases 



ASTRONOMY. 



towards the poles, because the circles to be 
described become less ; but in Great Britain it is 
still neariy 600 miles an hour. We are not 
sensible of this motion, because we and all our 
surroundings are carried along with it. It is in 
this way that the swift, but smooth and noiseless 
whirl which carries the earth's surface and its 
inhabitants eastward, makes the starry vault seem 
to flit past the eyes of these inhabitants towards 
the west. 

It is the earth's rotation that causes the vicissi- 
tude of day and night. The earth being a globe, 
only one-half of it can be in the sun's light at 
once ; to that half it is day, while the other half is 
in its own shadow, or in night. But by the earth's 
rotation, the several portions of the surface have 
'each their turn of light and of darkness. 

Length of a Day. — One complete rotation of the 
•earth does not make a day, in the usual sense. 
If the time is noted when a particular fixed star is 
■exactly south or on the meridian, when the same 
star comes again to the meridian the next day, 
the earth has made exactly one rotation, and the 
time that has elapsed is called a sidereal day. 
This portion of time is always of the same length. 
Sidereal time, or star-time, from its unvarying 
uniformity, is much used by astronomers. But 
the passage of a star across the meridian is not 
a conspicuous enough event for regulating the 
movements of men in general. It is not a 
■complete rotation of the earth, but a complete 
alternation of light and darkness that consti- 
tutes their day. This, which is called the natural 
or the solar day, is measured between two meri- 
dian passages of the sun, and is about four 
minutes longer than the sidereal day. The 
■cause of the greater length is this : When the 
«arth has made one complete turn, so as to bring 
the meridian of the place to the same position 
among the fixed stars as when it was noon the 
day before, the sun has in the meantime moved 
eastward nearly one degree among the stars, and 
it takes the earth about four minutes more to 
move round so as to overtake him. If this east- 
ward motion of the sun were uniform, the length 
•of the solar day would be as simple and as easily 



determined as that of the sidereal. But the 
ecliptic or sun's path crosses the earth's equator, 
and is therefore, more oblique to the direction of 
the earth's rotation at one time than another ; 
and besides, as the earth moves in her orbit with 
varying speed, the rate of the sun's apparent 
motion in the ecliptic, which is caused by that of 
the earth, must also vary. The consequence is, 
that the length of the solar day is constantly 
fluctuating ; and to get a fixed measure of solar 
time, astronomers have to imagine a sun moving 
uniformly in the celestial equator, and completing 
its circuit in the same time as the real sun. The 
time marked by this imagfinary sun is called mean 
solar time; when the imaginary sun is on the 
meridian, it is mean noon; when the real sun is 
on the meridian, it is apparent noon. It is obvious 
that a sun-dial must shew apparent time, while 
clocks and watches keep mean time. Only in 
four days of the year do these two kinds of time 
coincide. In the intervals, the sun is always 
either too fast or too slow ; and the difference is 
called the eqitation of lime, because, when added 
to or subtracted from apparent time, it makes it 
equal to mean time. The mean solar or civil day 
is divided into twenty-four hours, the hours into 
minutes and seconds. A sidereal day, we have 
seen, is shorter ; its exact length is 23 hours, 56 
minutes, 4 seconds of mean solar or common 
time. Astronomers divide the sidereal day also 
into twenty-four hours, which are, of course, 
shorter than common hours. In the course of a 
civil year of 365 days, the earth turns on its axis 
366 times, or there are 366 sidereal days. 

The earth, then, gliding noiselessly and steadily 
round on its axis, is the great time-keeper, and 
the heavenly bodies are the pointers or indices by 
which we note its progress. The art of reading 
off" the hour of the day from the heavenly bodies 
is necessary in the important problem oi finding 
the longitude at sea. 

The Seasons. — The way in which the earth's 
annual motion round the sun produces the alterna- 
tions of the seasons will be understood from the 
accompanying sketch, which represents a bird's- 
eye view of the earth's orbit as it woiUd be seen 





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1 


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B 


H 








1 


1 




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V7)<i^^ 


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from the north side. At the left of the figure, the 
earth is seen in the position it has at the winter 
solstice (21st December), the upper end of the 



axis, or north pole, leaning directly away from the 
sun at an angle of 23^° from the perpendicular to 
the plane. Thus, the sun's rays, which can only 



CHAMRERS'S INFOKMATION FOR IHE PEOPLE. 



fall on half the surface at once, reach only to the 
arctic circle ; and the turning of the earth on its 
axis has no effect to bring any part of the space 
within that circle into the light. On the north 
temperate zone, the sun's rays fall slanting and 
with little effect ; and the part within the light at 
any one time is small compared with the part 
in darkness, which causes short days and long 
nights. As the earth moves round in the direc- 
tion of the arrows, keeping its axis parallel to its 
original position — which it does on the principle 
of a spinning-top — more and more of the northern 
hemisphere comes within the light, until, at a 
quarter of the circuit, when the axis is at right 
angles to a line drawn from the sun, the rays fall 
direct on the equator, and reach to both poles, 
so that every part of the whole surface is twelve 
hours in light and twelve in darkness. This 
is the vernal equinox (22d March). In the con- 
tinued progress of the earth, the effect of the 
inclination of the axis is to turn the north pole 
towards the sun, instead of from it, and bring 
more and more of the northern hemisphere into 
the hemisphere of light ; and when the globe 
comes to the opposite point from where it started, 
the inclination is directly towards the sun, and its 
rays reach 23^° beyond the pole, so that the 
whole of the arctic circle turns round in continual 
day, and the temperate zone is longer in light 
than in darkness — it is midsummer (21st June). 
The earth's progress through the remaining half 
of its orbit has just the reverse effect on the posi- 
tion of the northern hemisphere with regard to the 
sun's rays ; at the middle of it there is another 
equality of day and night — the autumnal equinox 
(22d September) — and at the end, things are in the 
position from which they started. It is evident at 
a glance that the hemisphere around the lower or 
south pole must undergo the same vicissitudes as 
the northern, only in reverse order, the summer in 
the one corresponding to the winter of the other. 

The earth is in perihelion on the ist of January ; 
it is then about 3,000,000 miles nearer to the sun 
than on the ist of July ; the sun's disk is slightly 
broader, and we might expect this circumstance 
to mitigate the severity of our winter, and to add 
to the heat of summer in southern latitudes. But 
owing to the action of the law already given, by 
which the velocity of a planet increases with its 
nearness to the sun, the earth passes over the 
perihelion half of its orbit in less time than over 
the other half, and thus the effects of greater 
proximity are counteracted. 

It is this real motion of the earth in its orbit 
that causes the apparent motion of the sun in the 
ecliptic already described. If we conceive a wide 
circle, described outside the orbit, to represent the 
sphere of the fixed stars, when the earth is in its 
position marked 'winter,' the sun will appear to 
be at a point in this circle beyond the earth's 
'summer position; and as the earth moves to- 
wards the vernal equinox, the sun will seem to 
travel along the outer circle in the direction of 
the autumnal. It is to this plane that the orbits 
of all the other planets are referred ; they cross 
it at small angles, and the points of crossing are 
called nodes. 

A year, in the usual sense of the term, is the 

time that the s.un takes to move from either 

equinox back to the same equinox, or from either 

tropic back to the same tropic. This embraces a 

10 



complete circle of the seasons, and brings the 
earth into the same position with respect to the 
sun ; hence it is called a solar, equinoctial, or 
tropical year. If the equinoctial points remained 
fixed, this period would coincide with a complete 
revolution of the sun in the ecliptic, or — which is 
the same thing — of the earth in its orbit. But, 
owing to a cause which it belongs to physical 
astronomy to explain, the equinoctial points have 
a slow backward motion on the ecliptic of 50"^ 
annually ; when the sun, therefore, leaving the 
equinoctial point Aries one spring, arrives at that 
point next spring, he has yet 50" to travel before 
he has completed a circuit among the stars, which 
makes a sidereal year. The return of the sun to 
the same equinoctial point thus precedes its return 
to the same point in the ecliptic ; and this fact is 
known as the precession of the equinoxes. The 
length of the equinoctial or tropical year is 365 
days, 5 hours, 48 minutes, 50*4 seconds ; of the 
sidereal year, 365 days, 6 hours, 9 minutes, iO'4. 
seconds. 

The equinoxes thus retrograde 1° in 71 "6 years ; 
and in 25,868 years they will make a complete 
revolution of the ecliptic. Celestial longitudes 
being counted from the point Aries, are slowly 
increasing : since the first catalogues were formed, 
the longitudes of the fixed stars are all gjreater by 
30°. 

The Calendar. — How the civil year, which must ^U 
contain an exact number oi whole days, is adjusted ^f- 
to the natural year, which contains fractions of 2t 
day, is explained in CHRONOLOGY. 



THE MOON. 

Next to the sun, the moon is to us the most 
striking of all the heavenly bodies. Its disk is- 
almost equal to that of the sun, the mean apparent 
diameter being 31' 7". The real diameter is 2153, 
miles. 

The moon's orbit being elliptical, and the earth 
in one of the foci, its distance varies to the extent 
of 26,228 miles ; and this causes a corresponding^ ]J 
variation in its apparent diameter. The moon's 
disk is thus sometimes larger than that of the sun, 
so as to cause a total eclipse of the latter, when 
it passes over it. The moon's path in the heavens 
does not coincide with the sun's path or ecliptic^ 
but crosses it at two opposite points, at an angle 
of 5° 9'. These two points are called the moon's 
nodes. These points change their position, so as 
to make a complete revolution of the ecliptic, in 
a retrograde direction, in i8"6 years. When the 
moon is nearest to the earth, it is in perigee; and 
when at its greatest distance, it is in apogee. 

A month. — The moon goes round the earth in 
her orbit in about 27 J days ; and this motion 
makes her seem to us to move eastward among 
the stars at the rate of a little more than the length 
of her own apparent diameter in an hour. The 
time that the moon takes to make one complete 
revolution round the earth — that is, to return to 
the same place among the stars — is called a side- 
real month or lunation. But while the moon is 
performing this journey, the sun has also advanced, 
though at a slower pace, in the same direction ; 
and it takes the moon upwards of two days more 
to overtake the sun, as it were, and get again into 
the same situation with respect to that luminary 
and the earth. When it has done so, it has 



ASTRONOMY. 



I 



completed a synodic revolution. The synodic 
period or lunation, then, is the period between 
two new moons, or two conjunctions of the sun 
and moon ; it is the lunar month, and its mean 
length is 29 days, 12 hours, 44 minutes. The 
sidereal month is 27 days, 7 hours, 43 minutes. 

The moon, besides revolving round the earth, 
also turns on its own axis, and, by a remarkable 
coincidence, the rotation on the axis is completed 
in exactly the same time as the revolution in the 
orbit ; which is probably the case with all other 
secondary planets. In consequence of this coinci- 
dence, the same side of the moon is always turned 
towards the earth, as is evident from her surface 
presenting constantly the same easily recognised 
marks in the same positions. 

Phases of the Moon. — The light of the sun, 
falling upon the moon, is partly absorbed into its 
body ; but a small portion is reflected or thrown 
back, and becomes what we call moonlight. The 
illuminated part, from which we derive moonlight, 
is at all times increasing or diminishing to our 
eyes, as the moon proceeds in her revolution round 
our globe. When the satellite is on the opposite 




Phases ol the Moon 



A, B, C, D, F, G, H, K, appearances presented by the moon to an 
observer situated at the pole of her orbit ; A', B', C, D', P, G'. 
H', K', ' phases ' of the moon at the end of each eighth part of 
her course ; S, position of sun ; E, position of earth. 

side of the earth from the sun, or in opposition, 
we, being nearly between the two, see the whole 
of the illuminated surface, which we accordingly 
term full-moon. As the moon advances in her 
course, the luminous side is gradually averted 
from us, and the moon is said to wane. At length, 
when the satellite has got between the earth and 
the sun, or into conjunction, the luminous side is 
entirely lost sight of; the moon is then said to 
change. Proceeding in her revolution, she soon 
turns a bright edge towards us, which we call the 
new-moon. This gradually increases in breadth, till 
she is one quarter of her circuit from the sun, or 
in quadrature, when half the disk is illuminated, 
and it is then said to be half-moon. The luminary, 
when on the increase from new to half, is termed 
crescent (increasing) ; when between half and full, 
it is gibbous (hump-backed). 

In the early days of the new-moon, we usually 
see the dark part of the body faintly illuminated, 
an appearance termed the old-moon in the new- 
vtoon s arms. This faint illumination is produced 
by the reflection of the sun's light from the earth, 
or what the inhabitants of the moon, if there were 
any, might call earth-light. 

It is estimated that it would take 547,513 full- 
moons to give as much light as the sun ; which is 
twice as many as would find room in the whole 




The Moon, 
photographed.* 



half-sky. The moon's rays were till recently 
believed to be without heat ; but by concentrating 
them in a lens of three feet diameter, the Ita- 
lian philosopher Melloni obtained a sensible ele- 
vation of temperature. 

Tht physical condition of the moon is in many 
respects remarkable. As a powerful telescope 
shews an object as if it were 
a thousand times nearer 
than it is, we can view the 
moon as if it were only 
240 miles off, and thus the 
geography of its surface 
is pretty accurately known. 
The darker patches, which 
used to be considered seas, 
are found to be smooth) 
planes, and have all the 
appearance of having once 
been sea - bottoms. The 
brighter parts are mountainous. 

' The mountains of the moon are not mountains,, 
in the common acceptation of the term ; they are 
circular pits, hollowed out into the lunar substance, 
and surrounded by a ring-shaped elevated border, 
more or less abrupt and broken. There are some 
that are not more than 300 or 400 yards across ; 
others exceed 100 miles.' 

These circular mountains are denominated, 
according to their magnitudes. Walled Plains, 
Ring-mountains, Craters, and Holes. The most 
remarkable of the ring-mountains is that called 
Tycho, after the illustrious Danish astronomer. 
The enclosure is a circle forty-seven miles in diam- 
eter, and the inner side of the ridge is as steep 
as a wall, and 16,000 feet high, while the height 
above the surrounding surface outside is only 
12,000 feet. On the floor of the enclosed hollow 
stand a few isolated hills, one of them nearly a 
mile in height. 

The heights of the lunar mountains are measured 
by means of the shadows they cast during the 
phases. More than a thousand have been thus 
determined, several of which reach a height of 
23,000 feet. One peak named Dorfel is 26,691 
feet high. Considering that the moon's diameter 
is little more than one-fourth that of the earth, the 
lunar mountains are thus on a much grander scale 
than the terrestrial. The mountains of the moon 
have in many respects a volcanic character ; but 
no trace of an active volcano has yet been dis- 
covered. In addition to these ring-shaped hollows, 
there are long trenches with raised sides, called 
rilles, and bright rays, proceeding from a centre, 
like cracks, the nature of which is a mystery. 

The moon is ascertained to be without any 
atmosphere ; nor is there the least appearance of 
liquid of any kind, although the surface would 
seem to have been at one time partly covered with 
water. The direct rays of the sun will thus shine 
for fourteen days with a fierceness far beyond 
anything experienced on the earth ; but there can 
be no accumulation of heat, and on the unillu- 
minated side the cold must be for other fourteen 
days more rigorous than on the summits of our 
loftiest mountains. The present cold and dead 
appearance of the moon's surface, compared with 
what it must once have been, is accounted for by 
supposing that the original heat of the moon, 

• Copied by permission of Messrs Smith. Beck, and Beck, from 
Warren De la Kue's photograph 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



owing to its small size, has been dissipated into 
space. 

The Moon and the Weather.— \\ is an almost 
universal belief that the changes of the moon 
influence the weather ; but when put to the test 
of accurate observation, this opinion is found to be 
completely groundless : there is, in fact, no cor- 
respondence whatever between the changes of the 
moon and those of the weather. See Meteor- 
ology. 

eclipses. 

Eclipses are caused by the positions of the earth 
and moon with respect to each other and to the 
sun. An eclipse of the sun takes place when the 
moon is between the sun and earth ; and an 



eclipse of the moon is the result of the earth being 
between the sun and moon. 

The accompanying figure represents two posi- 
tions of the moon : in the one she is in the earth's 
shadow, and totally eclipsed ; in the other, her 
shadow is falling upon a part of the earth's surface, 
and eclipsing the sun to that part. Within the 
limited circle on which the moon's shadow, or 
umbra, falls, no part of the sun is seen, or he is 
in total eclipse ; within a larger space round that 
spot, the moon seems to cover only part of the 
sun's disk, making a partial eclipse ; and this 
space is within the pemmibra, as it is called. 
When the moon happens to be so far distant from 
the earth that the cone of the shadow falls short 
of the earth, then a spectator standing immediately 
under the apex, or point, sees the moon covering 




the middle part of the sun's disk, and leaving a 
ring of it visible. This is an annular eclipse. 

It is only when the moon is in one of her nodes, 
or within a limited distance from it, that there can 
be an eclipse either of sun or moon. Now, the 
motions of the two orbs are such that there must 
be annually two solar eclipses, and there may be 
four. The limits for a lunar eclipse are shorter, 
and a whole year may elapse without one occur- 
ring. There are thus more solar eclipses than 
lunar, though the general impression is to the 
contrary. This arises from the circumstance that, 
whenever an eclipse of the moon occurs, it is seen 
at all places where the moon is above the horizon, 
and the atmosphere unclouded ; whereas an eclipse 
of the sun is confined to a limited tract. 

These eclipses, like all other things about the 
heavens, can be predicted with almost perfect 
accuracy. It is also possible to calculate 
backwards, so as to find the probable date of 
remarkable eclipses recorded to have happened 
in antiquity. 

The inferior planets, Mercury and Venus, some- 
times cross the sun's face, on which occasion they 
may be traced by a telescope as a dark speck 
moving from one edge over to another, and then 
disappearing. These are transits, and are of 
importance in ascertaining the sun's parallax and 
distance. 

In times when people's fates and fortunes were 
predicted from the positions of the planets at the 
hour of their birth, much stress was put upon 
conjunctions and oppositions. When two bodies 
are in the same quarter of the heavens, so as to 
be near one another, or have the same longitude, 
they are said to be in conjunction ; when they are 
half a circle apart in longitude, they are in opposi- 
tion. Astronomers use the sign ^ to indicate con- 
junction ; and ^ to indicate opposition. 

COMETS. 

* Comets,' says Humboldt, * at the same time 
possess the smallest mass, and occupy the largest 
space of any bodies in the solar regions ; in their 
number, also, they exceed all other planetary 

12 



bodies, except, perhaps, aerolites, amounting to 
many thousands at least.' Comets have usually 
two parts — a body or head, and a tail. The head 
has the appearance of a round nebulous mass of 
light, with usually a brighter part in the centre 
called the nucleus, but so far from containing any- 
thing solid, that the smallest stars are seen through 
the densest part of the substance. The tail is a 
still lighter luminous vapour, surrounding the 
body, and streaming far from it in a direction 
generally opposite to that in which the sun is 
situated, as if repelled by that luminary, and often 
curved. A vacant space has been observed 
between the body and the enveloping matter of 
the tail, which also appears sometimes less bright 
along the middle, immediately behind the head, 
as if it were a stream which the head had parted 
in two. 

Unlike planets, comets shine partly, at least, by 
their own light, and are believed by some to be 
masses of white-hot gas. Others suggest a connec- 
tion between comets and the rings of small bodies 
that produce meteoric showers (see Meteor- 
ology). The tail is by no means essential to a 
comet ; by far the greater number have no such 
appendage, appearing merely as a nebulous disk. 

With regard to the motions of the comets, 
instead of revolving, like the planets, nearly in 
the plane of the sun's equator, it is found that 
they approach his body from all parts of sur- 
rounding space. At first, they are seen slowly 
advancing, with a comparatively faint appearance. 
As they approach the sun, the motion becomes 
quicker, and at length they pass round him with 
very great rapidity, and at a comparatively small 
distance from his body. The comet of 1843 
approached within one-seventh of his radius. 
When near the sun, their brilliancy is greatly 
increased. 

In moving round the sun, comets obey the same 
general laws that regulate the planets. They do 
not, however, all describe ellipses ; some pass 
through our system in parabolas, open curves, 
which never return into themselves. Now, the 
comets that move in shut orbits, or ellipses, 
must return to the sun again and again, and may 



ASTRONOMY. 



therefore be considered as members of the solar 
system. The others are only casual visitors ; 
unless they meet with something to alter their 
orbits, they can never return, but must run off 
into the immensity of space. 

The most remarkable of the comets ascertained 
to return is one usually denominated H alley's 
Comet, from the astronomer who first calculated 
its period. It revolves round the sun in about 
seventy-seven years, its last appearance being at 
the close of 1835. The annexed cut represents 



some of the various appearances it presented on 
that occasion in different parts of its orbit — a, b 
c, in approaching the sun ; d, e, in retreating. 

Another, called Encke's Comet, from Professor 
Encke of Berlin, has been found to revolve once 
in 3i years ; but in this case the revolving body 
is found, at each successive approach to the sun, 
to be a little earlier than on the previous occasion, 
owing probably to a cause to be afterwards de- 
scribed. A third, named Biela's Comet, revolves 
round the sun in 6^ years. It is very small, and 




has no tail. During its visit in 1846, this comet 
was seen to separate into two distinct comets, 
which kept moving side by side, till they disap- 
peared. On the return of the comet in the autumn 
of 1852, the distance between the two nuclei had 
much increased. In 1770, a comet got entangled 
amidst the satellites of Jupiter, and was thereby 
thrown out of its usual course, while the motions 
of the satellites were not in the least affected by 
its proximity. This proves the extreme lightness 
of the matter composing comets. 

The comet now called Halle/s, at its appear- 
ance in 1456, covered a sixth part of the visible 
extent of the heavens, and was likened to a Turkish 
scimitar. That of 1680, which was observed by 
Sir Isaac Newton, had a tail calculated to be 
60,000,000 miles in length — a space two-thirds of 
the distance of the earth from the sun. There 
was a comet in 1744 which had six tails, spread 
out like a fan across a large space in the heavens. 



PHYSICAL ASTRONOMY. 

Not long after Kepler had made those remark- 
able discoveries which completed the view of the 
regular courses and periods of the celestial 
motions, the causes of the motions, or the forces 
whereby they are sustained, were also discovered 
by Sir Isaac Newton. He was the first to shew 
that the vast planetary balls whirl about their own 
centres, and fly through the celestial spaces, on 
exactly the same principles as a cannon-ball or 
a stone moves when thrown into the air. The 
principles of celestial mechanics, therefore, are 
the principles of motion discovered from the 
observation of bodies on the earth ; they are 
the three Laws of Motion and the doctrines of 
the Composition of Forces, as illustrated under 
Matter and Motion, and the doctrine of 
Universal Gravitation. 

The fall of unsupported bodies to the earth is 
the most familiar action in nature ; but it is not 
two centuries since Newton discovered that this 
action extends to the moon, the sun, and the 
planets. He proved that the moon is constantly 



falling towards the earth, and would fall into it, 
but for another motion she has, which is always 
carrying her off, and would of itself shoot her far 
away into space in a straight course ; so that her 
actual circuit is the balance of two forces — one her 
weight, or gravity, towards the earth {centripetal 
force), the other an undying impulse to fly off at 
a tangent, like a whirled stone when the sling is 
let go {centrifugal force). 

It was through the application partly of the laws 
of motion, and partly of Kepler's laws, that Newton 
established the universal prevalence of gravity. It 
being once found that the planetary motions could 
be kept up by a combination of forces ; that is, by 
a force that projected the body once for all into 
free space with a great velocity, which, by the first 
law of motion, would be always kept up, whether 
it went off straight through space, or were com- 
pelled to go round a circle — and some second 
force to hold it in that circle ; the great question 
arose : What is the cen- 
tral force — what power 
is it that causes the 
moon to fall towards 
the earth, instead of 1 

running off; and in like \ s' / \a. 

manner obliges the 
planets, with their im- 
mense speed, to keep 
constantly falling to- 
wards the sun ? A planet P, if not held in by 
some tie, would fly off along PA, instead of being 
always carried round the sim S. 

Newton proved by mathematical reasoning, from 
the Jirst law of Kepler, that the deflecting force 
points exactly to the sun, and is therefore likely 
to be lodged in his body. From Kepler's second 
and third laws, he proved that the force is in- 
versely as the square of the distance ; and, finally, 
he shewed that the deflection of the moon from a 
straight line is exactly equal to the fall of a stone, 
if it were at the distance of the moon. The moon 
being sixty times farther off from the earth's 
centre than we are, gravity is there 3600 times 
weaker ; so that the speed acquired by a stone 
falling one second near the earth's surface, would 




CHAMBERS'S INFORMATION FOR THE PEOPLE. 



be acquired only by falling an hour at the height 
of the moon. And it can be easily proved by 
calculation that the falling action of the moon is, 
in an hour, exactly that of a stone in a second. 
It being thus shewn that the moon is deflected by 
gpravity, it was then concluded that the planets are 
deflected to the sun by the same cause ; or that 
gravity is the great central force throughout the 
solar system. 

After thus identifying the mechanical causes of 
the planetary motions, Newton deduced all the 
laws of Kepler from the combination of the two 
great forces of Gravitation and Straight Impulse. 
In this way he found that these laws are not 
strictly tnie, as given by Kepler, and that therefore 
the prediction of the places from them could not 
be perfectly accurate. Not only was the sun's 
centre not the true focus of the ellipse, that being 
the common centre of gravity of the sun and the 
planet, but he shewed that not one of the paths 
is an exact ellipse. If there were only one planet 
to the sun, that planet would describe a perfect 
ellipse ; but if a second planet is introduced, this 
planet is not only attracted by the sun (and the 
sun attracted by it), but there is an attraction 
between it and the first planet which disturbs the 
motion of both. 

In Uke manner, if the moon and the earth were 
alone in the universe, the moon would go round 
the common centre of gravity of the two in a 
perfect ellipse ; but as both move round the sun, 
and he acts upon both, very great deviations take 
place from the elliptic orbit ; in fact, the applica- 
tion of Kepler's two first laws to the moon could 
never predict her place with anything like accu- 
racy. 

Perturbations. — But the same discoveries that 
shew the defects of Kepler's laws, give the means 
of correcting those defects, or of calculating the 
disturbing influences, so as to predict what the 
real motions will be under those disturbances. 
The special disturbances are known as perturba- 
tions or inequalities. In calculating them, astro- 
nomers first suppose the case of one body revolving 
about a second, and disturbed in its regular orbit 
by a third ; this is what is called the problem of 
the three bodies; the disturbing effect of each 
separate cause being thus found, the whole are 
then combined. 

Masses of the Heavenly Bodies. — The theory of 
universal gravitation gives us the means of com- 
paring the weights of the heavenly bodies, as if 
they were weighed on a steelyard. Thus the fall 
of the earth towards the sun in an hour can be 
compared with the fall of the moon to the earth in 
an hour ; and the two quantities, multiplied by the 
squares of the two distances, will give the propor- 
tion between the mass of the sun and the mass of 
the earth, which is about 314,760 to i. When we 
remember that the bulk of the sun exceeds that of 
the earth more than a million of times, we see that 
the matter of the sun is much lighter than the 
material of the earth. In the same way, Jupiter's 
mass is found to be 301 times that of the earth. 

To find the actual density or specific gravity of 
the different bodies of the solar system, and com- 
pare it with a fixed standard, such as water, it is 
necessary to know the average density of the 
whole earth. This has been sought by comparing 
the attraction' of some known body with the 
attraction of the globe. Thus, Dr Maskelyne 

14 



attempted to calculate the attraction of a moun- 
tain in Perthshire, by finding how far it made a 
plumb-line to deviate from the perpendicular. In 
this experiment the plumb-ball was supposed to 
be attracted downwards by the general mass of 
the earth, and sideways by the mountain ; and it 
could thus be seen how many times the whole 
earth surpassed the mountain in gravitating force. 
If the mountain itself then were measured, and its 
composition ascertained, so as to give the density 
of its rocky material, the entire mass of the moun- 
tain would be obtained, and from that the entire 
mass of the earth. The result of this experiment 
was, that the earth is, on an average, \\ times 
denser than water, or more than twice the density 
of granite or sandstone rock. Other experiments, 
of a different kind, have given much the same 
determination. From this we can estimate the 
densities of the sun, moon, planets, and satellites. 
The Figures of the Heavenly Bodies^ how caused. 
— It has already been seen that the sun and 
planets are, in general, round masses, with a slight 
flattening, which seems to be connected with the 
rapidity of their whirl Now, both the general 
roundness and the flattening can be shewn to 
arise from ordinary mechanical laws, such as we 
see operating on the earth, provided we suppose 
that the planets were at one time soft, fluid masses. 
If a fluid mass of attracting particles be left to 
itself — that is, if there be no external compulsion, 
either attraction or pressure — it will always assume 
the round shape. 

But if such a body is whirled, the matter at 
the surface acquires a tendency to fly off, so 
as to oppose the general attraction towards the 
centre. If the whirled body is soft or liquid, 
it cannot remain at rest, or in equilibrium, in 
its round form, inasmuch as the matter at the 
equator, having a greater velocity than elsewhere, 
is rendered lighter by its centrifugal tendency, 
and is not a sufficient balance for the matter at 
the poles. To restore the balance, there must 
be a greater depth from the equator to the centre 
than from the poles to the centre ; in other words, 
the equatorial width must exceed the polar width, 
which is what we actually find in all the revolving 
bodies. The planets also that revolve the most 
rapidly, as Jupiter and Saturn, are found to be the 
most elliptical. 

Precession of the Equinoxes. — It has been al- 
ready explained in what this consists. The cause is 
to be found in the combined action of the sun and 
moon on the protuberant mass of matter accumu- 
lated at the earth's equator. The exact nature of 
this action is too complex for description here ; but 
combined with the rotation of the earth on its 
axis, the result is the regression of the equinoctial 
points above mentioned; while, as a necessary 
consequence, the celestial pole describes, at the 
same rate, a circle among the stars round the pole 
of the ecliptic at a distance equal to the obliquity 
of the ecliptic. Its motion, however, is not quite 
uniform or straight, but in a waving line, alter- 
nately approaching and receding from the pole of 
the ecliptic. This secondary disturbance, which 
is caused by the fluctuating position of the moon's 
nodes, is known as the nutation of the earth's 
axis. 

The poles of the earth do not, then, point always 
to the same places among the stars. The present 
position of the north pole is within a degree and 



ASTRONOMY. 



A half of a bright star in the constellation of the 
Lesser Bear. Its motion will bring it gradually- 
nearer until it is within half a degree of that star, 
^fter which it will recede from it. Its course may- 
be traced by drawing a circle on a celestial globe 
round the north pole of the ecliptic, at the distance 
of 22^. The celestial pole describes this circle in 
25,868 years. Twelve thousand years hence, it will 
be near one of the brightest stars in the heavens, 
•called a Lyrae, which will then be the pole-star. 

Stability of the System. — It is natural to inquire 
whether the numerous perturbations which all the 
bodies are subject to, are such as in the long-run 
to overthrow the present arrangements of the 
system. Now, so far as has yet been positively 
ascertained, the total effect of all the mutual dis- 
turbances has no such tendency. Though there 
are secular variations that may go on increasing 
for thousands of years, it has been shewn that they 
-will decrease continually for periods of like dura- 
tion, and the limits within which this secular 
oscillation is confined are in all cases extremely 
narrow. 

Two causes are pointed to as likely to produce 
■permanent changes in the planetary motions, i. 
It is generally held by philosophers, that space, 
instead of being perfectly empty, is everywhere 
filled with an exceedingly thin medium, which they 
<;all ether. Now, however slight the resistance this 
may offer to bodies moving in it, yet, if it exist at 
all, it must tell in the end, and will have the effect 
of contracting the orbits of the planets, and bring- 
ing them nearer and nearer to the sun. Such an 
effect would be most powerful in the case of light 
bodies like comets ; and, accordingly, some of the 
short-period comets have been observed to return 
to the sun in a shorter period each successive 
revolution. In the case of the planets, no such 
effect has yet been appreciable, owing to their 
much greater mass. 2. The tidal wave moves 
westward on the earth's surface, contrary to the 
direction of the earth's daily motion; it is thus 
believed to act like a friction-break on a wheel, 
rendering the daily rotation slower, although by a 
<iuantity so small, that it has not yet been ascer- 
tained with certainty. 



SIDEREAL ASTRONOMY— THE FIXED 
STARS. 

The first thing that strikes us about the stars is 
their difference as to brightness. They can be 
-classified according to this feature. The most 
brilliant are said to be of the first magnitude; the 
next of the second ; and so on. The smallest stars 
visible to the naked eye are of the sixth or seventh 
magnitude. The number of stars visible in one 
hemisphere may be about 2000, making in all 
4000. About twenty-four are reckoned of the first 
magnitude. By using telescopes, a vast mass of 
new stars come into view, which are reckoned as 
far as the seventeenth magnitude; the numbers 
and closeness increasing with every increase of 
the telescope's power. 

From the earliest times, the stars have been 
divided into groups called constellations, which 
were named from fancied resemblances to animals 
or other figures. Thus, a group in the northern part 
-of the sky is called Ursa Major., or the Greater Bear. 
■From the figure of the seven more conspicuous 



stars, it is sometimes called the Plough. Another 
well-marked group is called after the mythical 
personage Orion. Individual stars are indicated 
by the letters of the Greek alphabet or by numbers, 
as « Ursa Majoris (in the tip of the tail of the 
Greater Bear), 24 Comae. Some remarkable stars 
have names, as Aldebaran (« Tauri), Sirius (in the 
nose of Canis Major). By means of a celestial 
globe, or a set of star-maps, the more conspicuous 
constellations may be soon recognised. 

The stars are believed to l^ so many suns, 
shining by their own light, and being each per- 
haps the centre of a system of planets, the abodes 
of sentient and intelligent existence. Their im- 
mense distance reduces them all equally to mere 
points of light ; in the most powerful telescopes 
they shew no disk, and differ from one another, 
not in magnitude, properly speaking, but in bril- 
liancy. Notwithstanding this seeming inaccessi- 
bility to observation, the spectroscope makes 
known to us with almost certainty not a few facts 
regarding their physical constitution. They have 
white hot cloudy photospheres like the sun, and 
contain pretty much the same substances; thus 
Sirius has been ascertained to contain sodium, 
magnesium, iron, and hydrogen. 

For a long time the distances of the fixed stars 
were believed to be immeasurable. More refined 
modes of observation have recently detected the 
parallax of several stars, and determined positively 
how far off they are. To state these distances in 
miles conveys no idea. It is better to take some 
large unit, such as the distance light travels in a 
second, which is 1 86,000 miles ; we can then give 
the distance of a star in the time its light takes to 
reach us. The sun's distance is sometimes taken 
as a standard. The nearest distance yet measured 
is that of a fine double star in the southern hemi- 
sphere {a. Centauri), calculated at 224,000 distances 
of the sun, which it takes light three and a half 
years to traverse. ' From the measurements al- 
ready made, we may say that, on the average, 
light requires fifteen and a half years to reach us 
from a star of the first magnitude, twenty-eight 
years from a star of the second, forty-three years 
from a star of the third, and so on, until, for stars 
of the twelfth magnitude, the time required is 3500 
years.' — Lockyer's Astronomy. 

Variable Stars. — Some stars undergo periodical 
increase and diminution of lustre, and are known 
as variable stars. There are several instances 
also on record of stars which have come into sight 
for a time, and then gradually vanished, to which 
the name of temporary or new stars has been 
given ; the latter phenomenon, however, is no 
doubt only an extreme case of the former, the 
period being long, and the diminution of lustre 
excessive. The star Omicron, in Cetus, is a re- 
markable instance of a variable star. It goes 
through a series of variations in a period of about 
330 days. 

The analogy of our sun is thought to afford 
an explanation of this phenomenon. The sun is 
clearly a variable star, his light and heat varying 
with the increase and diminution of the spots on 
his surface, which follow, as we have seen, a 
period of ten years. The observations of Balfour 
Stewart and others go far to prove that the fre- 
quency of sun-spots is regulated by the position 
of the nearer planets. Mr Stewart holds that * the 
approach of a planet to the sun is favourable to 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



increased brightness, and especially in that por- 
tion of the sun which is next the planet.' We 
have only, then, to suppose that a variable star has 
a very large planet revolving round it at a short 
distance ; this will cause the part next the planet 
to be brighter than the rest ; and thus the star will 
vary with a period equal to that of the planet. 

Double and Multiple Stars. — Another variety in 
the nature of these luminaries is their being in 
some instances not single stars, as they appear to 
the naked eye, but a group of two or more, evi- 
dently, from their motions, forming one system. 
The star Castor, one of the Twins, is found, when 
much magnified, to consist of two stars, of between 
the third and fourth magnitude, within five seconds 
of each other. Upwards of 6000 such groups have 
been observed. It is generally observed that they 
move round each other within a certain time, and 
in elliptical orbits; the revolution of Castor, for 
instance, is supposed to be accomplished in 252 
years. 

Proper Motion of Stars. — When we speak of 
the stars beingyfx(f</, it is only as compared with 
the planets. There is no such thing as absolute 
fixity in the universe. Besides the revolutions of 
the double stars, a great many stars have been 
observed to be slowly but constantly carried away 
from their places in the heavens. This proper 
motion, as it is called, has in one instance shifted 
the situation of a star in the heavens, in the course 
of fifty years, over iV^h of a degree. Founding 
upon these displacements of the stars, it has been 
concluded that our sun, accompanied by his 
attendant planets, is in motion towards a region 
of space m the direction of the constellation 
Hercules. 

Milky-way. — The stars are very unequally scat- 
tered over the sky. We may always observe a 
whitish band arching the heavens, called the 
Milky-ivay, which appears to the eye, and still more 
to the telescope, as a dense mass of starry dust. 
From this apjiearance it is inferred that the stars 
forming our firmament do not extend indefinitely 
into space, but are limited in all directions, the 
mass having a definite shape. Herschel conceived 



the stratum to be thin in proportion to the length 
and breadth, and that looking through the mass of 
stars forming the depth in these directions, gives 
the appearance of the Milky-way. As the Milky- 
way divides into two branches, there must be a 
bifurcation of the stratum. Our place in the 
system is conceived to be not in the centre, but 
nearer to one end and to one surface. 

Remote Star-systems, Nedul<z.— From the grand 
idea of the solar system, we thus rise to the vastly 
grander idea of a stellar system, composed of 
countless myriads of solar systems, many of them, 
perhaps, surpassing our own in magnitude, and 
held together by the universal bond of gravitation. 
But this star-system, which we may call our own 
universe, inconceivably vast as it is, is but an 
item of the heavenly inventory. Far beyond its 
bounds, the modem telescope has descried similar 
systems in great numbers, each hanging in some 
tolerably defined shape in the depths of space. 

A few of these remote systems are visible to 
the naked eye, as faint luminous spots in the 
heavens ; but by means of powerful telescopes, 
thousands of them have been observed and cata- 
logued. They are generally spoken of collectively 
as nebulce, from their cloud-like appearance. Many 
of them are resolvable into individual stars, even 
with a moderate telescope, but others were found 
to resist even the powerful telescope of Sir 
William Herschel ; and he accordingly made a 
distinction between clusters of stars, or resolvable 
nebulae, and nebulae properly so called, which 
presented no appearance of stars. These last 
were conceived to be elementary sidereal matter 
in a diffused and gaseous form — matter in the 
course of being condensed to stars and systems. 
But when the still more powerful telescope of Lord 
Rosse shewed that several so-called nebulae, 
hitherto irresolvable, were really groups of stars, 
the nebular theory was thought to be overturned ; 
for although many still resisted resolution, this 
was attributed to extreme distance, and the want 
of sufficient telescopic power. That wonderful 
instrument, the spectroscope, however, has recently 
reinstated the nebular theory, by shewing that 




Nebulae and Clusters. 



among these appearances there are real nebulae, 
devoid of solid or liquid matter, and consisting 
of masses of glowing gas — apparently nitrogen 
and hydrogen. 

These nebulous-looking objects, whether star- 
clusters or true nebulae, present the most remark- 

16 



able and sometimes startling shapes, of which a . 
few specimens are represented in the figure. Itj 
is believed that Lord Rosse's telescope has brought, 
within our ken objects whose light must take sixty 
thousand years to reach us ! 



GEOLOGY. 



I 



NATURE OF THE SUBJECT. 

WE have most of us stood at the base of a 
great cliff, and looked upwards with awe 
at the rocks exposed on its weathered front. Such 
a sight might suggest many strange and interesting 
inquiries. How did these rocks come to be where 
they are? Of what are they composed? When 
were they formed ? Whence the material for the 
vast thickness of rock that composes the crust of 
the earth? Whence have come the varied sub- 
stances that form our limestones, coals, and sand- 
stones ? Whence also the strange shells, plants, 
and animals that a closer examination of their 
structure reveals? Are these the remains of 
bygone living organisms, or are they only marks 
in the rocks themselves ? If they were once living 
creatures, what were their structure and habits? 
Such questions suggest themselves to every think- 
ing person, and such questions Geology undertakes 
to answer. 

Geology, from the Greek ge, the earth, and logos, 
a description, is, according to its name, a descrip- 
tion of the earth. It examines the various rocks 
that compose its crust, and seeks to explain their 
appearance, form, structure, relative position, for- 
mation, age, and distribution throughout the globe. 
It also inquires minutely into their contents, 
animal, vegetable, and physical ; the causes of 
their imprisonment in their stony tombs ; and the 
structure and habits of the creatures there found. 
It pictures forth the physical history of the globe 
during the successive epochs through which it has 
passed, with their varied scenery and inhabitants, 
the formation of its many strata, and the structure 
and progress of the organic forms that successively 
waved in its atmosphere, moved over its surface, 
or swam in its seas. In short, it is the province 
of geology to describe the whole natural history 
of the globe during the various ages of the long 
past ; and it includes the ancient zoology, botany, 
mineralogy, and geography of the earth, whose 
present conditions are the result of the numberless 
changes through which it has passed in these 
geological eras. The past it seeks to interpret 
solely by the present, assured that the laws of 
nature are invariable and universal, and that 
causes operating now produced like effects in the 
primeval earth. 



ROCKS, THEIR KINDS, STRUCTURE, AND 
DISPOSITION. 

In order to speak with precision in our study 
of this subject, it is necessary to have a distinct 
idea of what a rock is in geology, and to under- 
stand certain things regarding the kinds, structure, 
and arrangement of rocks. 

What a Rock is in Geology. — In geology, the 
word rock has a wider meaning than it has in 
common language, where it means a mass of stone 
of considerable size. In this science, the word 
rock is used to designate any of the materials 
that compose the crust of the earth, of whatever 
size and softness they may be. Geologists reckon 



sandstone, marble, quartz, granite, and limestone 
to be rocks, as others do ; but they also speak 
of coal, gravel, chalk, sand, salt, peat, and hke 
soft and broken substances, as rocks or rock- 
formations. 

Kinds of Rocks. — Rocks have different names, 
according to their appearance and structure. 
Every one knows what sand is, and that it varies 
greatly in fineness. The most of the sand we see 
is composed of small particles of rock ground to 
powder, but it often consists, as we shall after- 
wards learn, of numberless very minute shells. 
Sandstone is the usual rock of which houses are 
built, and which, in thin layers, is used for pave- 
ment. This rock is more common than any other, 
and has many varieties, and is, of course, so called 
because it is composed of particles of sand that 
have been made to cohere. When the particles 
of the sandstone are somewhat larger and sharper, 
the rock is called grit, from the particles having 
been grated down or broken : the rock of which 
millstones are formed is called millstone-grit, and 
its value depends on the hardness and sharpness 
of the grains of which it is composed. When the 
particles are larger still, and form small stones 
that do not cohere, the rock is called gravel; and 
when yet larger and more rounded, shingle, 
examples of both of which occur on the sea-beach. 
A mass of broken angular stones thrown up in a 
heap, as by a river after a flood, is called rubble. 
A stone when small is called z. pebble ; when large, 
a block; and when rounded and worn, a boulder, 
because it is ^^//-shaped. The fine sediment at 
the bottoms of rivers, lakes, and pools is composed 
of ground mineral, animal, and vegetable matter. 
When this is tough and plastic, it is called clay, 
because it cleaves or sticks ; and the whole accumu- 
lation of mud, clay, and sand at the bottom of any 
water, is called silt. 

The remains of vegetable matter found in various 
parts of the country, and used as fuel, are known 
as peat; and coal is nothing but such vegetable 
matter changed by heat, and hardened into rock 
by pressure. Limestone is the name given to the 
hard rock which, after being burned in a kiln, 
forms lime. When the limestone is hard and 
crystalline, it forms marble, which is of different 
colours, from deep black to pure white, and often 
beautifully variegated. Chalk is a variety of lime- 
stone, and obtains its name from this fact; the 
word chalk being another form of the Latin calx, 

Common slate, used for wntmg on and for 
roofing, is composed of thin layers of hard rock, 
of which some of our highest mountains are formed. 
The name shale is applied to a kind of rock which 
shells off or splits into very thin layers, and which 
may be seen in great heaps near coal-pits. Thin 
layers of sandstone used for pavement are called 
flags. The white pebbles so common on the sea- 
beach, and so easily broken, are made of quarts, 
and rock formed of it is called quarts-rock. Some 
varieties of quartz, called rock-crystals, are very 
beautiful and valuable, and are reckoned precious 
stones, such as agate, amethyst, and topaz. J^^'"^ 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



has much the same composition as quartz, and is 
very plentiful in chalk. The granular rock brought 
from Aberdeen and elsewhere, so beautiful when 
polished, is called granite, from its being com- 
posed oi grains of other rocks. It has two chief 
varieties, the gray and the red, according to the 
prevailing mineral in its composition. It is com- 
posed of quartz, mica, and felspar. It composes 
the mass of some of the chief mountain ranges, 
and forms part of some of the grandest scenes in 
nature. It is in general of igneous origin, but is 
certainly not always such ; its origin is the subject 
at present of much controversy. The particles 
that glitter like silver in the granite are pieces of 
w/V<V which is so named because it shines. A 
mineral very like mica in appearance, but different 
in composition, is called talc, from its feeling 
somewhat greasy or tallowy when touched. 

The molten matter th^i flows from volcanoes is 
called lava ;^ pumice-stone^ is the cinder of such 
discharges ; while the ashes that are thrown into 
the air are called scoria. In geologic times also 
there existed volcanoes from which lava issued ; 
the rock this lava formed is called trap,* from 
lying in j/^/r-like masses, as it flowed from the 
mountain ; and one kind, whinstone, which is 
much used for roads. A common variety is known 
as greenstone, from its colour, of which Salisbury 
Crags, near Edinburgh, are composed. Another 
variety is called basalt, and is generally found in 
columns standing close together, which often form 
wonderful naturaJ scenes, such as Fingal's Cave 
and the Giants' Causeway. Another variety is 
porphyry,^ so called from its frequent purple colour, 
and is easily distinguished by its granular appear- 
ance. A kind of light porous rock, formed of 
cohering volcanic ashes, is known as trap-ttiff, or 
tufa, a word that comes from Italy, the seat of so 
much volcanic action. 

Structure of Rocks.— On examining the 
rocks forming the crust of the earth, we find that 
they may be divided into two great classes — the 
stratified, or those deposited in strata or layers ; 
and the unstratifitd, or those not so formed. Sand- 
stone and slate are stratified rocks ; granite and 
trap are unstratified. 

I. Stratified Rocks. — Any thin deposit of rock 
is called a layer, from its having been laid down 
under water; a bandy from its being like a thin 



band ; a bed or a stratum, when of greater thick- 
ness, from Latin sterno, to spread ; and a seam^ 
when of a peculiar character as compared with 
the rocks near it, as a seam of coaL Stratum^ 
with the plural strata, is the general term for any 
layer of rock, and hence all rocks in layers are 
said to be stratified. Rocks that split up into 
very thin layers, a great number being included 
in the thickness of an inch, are said to be lami- 
nated, and the thin layers are called lamince ; 
these are formed by deposition. Slate-rocks have 
a remarkable tendency to split or cleave in one 
direction, which is called their cleavage. This in 
general does not coincide with the lamination, and 
may be at any angle. It is by the cleavage that 
the slates of commerce are separated. Some 
attribute this phenomenon to pressure, others to 
heat. Gneiss and other rocks have a tendency to 
split ox foliate'^ into thin layers of different miner- 
alogical character, as quartz, mica, and such like. 
This is called their foliation, and must be distin- 
guished from their stratification and also from cleav- 
age, which exists in rock of one mineral composi- 
tion. Granite and other rocks are often split into 
large masses, more or less cubical, along certain 
lines at equal or varying distances. These lines of 
separation are CdXled. joints. They occur much in 
igneous rocks, as in basalt. These words should 
be carefully distinguished : thus shales are lami- 
nated ; schists, foliated ; igneous rocks, jointed ; 
slates, subject to cleavage. When a rock is com- 
posed of rounded pebbles or boulders imbedded 
in other matter, it is called a conglomerate, and 
sometimes, from its appearance, pudding-stone or 
plum-pudding stone. 

2. Unstratified Rocks. — Unstratified rocks 
assume various forms, according as they have 
been shot up amongst the stratified rocks ; for, as 
we shall afterwards see, they have been erupted 
from volcanoes. Very often, like most volcanic 
substances, they zxe porous or cellular, like pumice- 
stone ; frequently they form gigantic columns, when 
they are said to be columnar, like basalt ; and 
often they are found in large globular or spherical 
masses, like bombs or cannon-balls. 

Disposition of Rocks. — i. Stratified Rocks. 
— When rocks lie parallel to the horizon, they are 
termed ^a/ or horizontal, as A, in the following 
section ; when at an angle to it, they are said to 




Section of the Different Kinds of Strata. 



A, Horizontal and unconform- 

able rocks. 

B, Inclined strata. 

C, A slip. 

D, A disrupting mass. 

E, Overlying trap. 

F, Interstratified trap. 



G. A dike. 

H, Bent and rolling strata. 

I, A basin or trough. 

K, A ridge of rocks. 

L, The dip of the rocks, 45*. 

M, An outcrop. 

N, Veins. 



O, A fault. 

P, Contorted or twisted strata. 

Q, A seam. 

K, Rocks tilted up. 

S, Columnar basalt 

T, Conglomerate. 



U, Limestones. 

V, Granite, disrupting. 

W, Trap. 

X, Sandstones. 

Y, Coal. 

Z, Silt or graveL 



be inclined or dipping, as B ; when one end has 
been thrown up by some other mass, they are 

' From Latin mico, to* shine. * From Swedish trappa, a stair. 

' From Latin lavo, to lave or flow. * From GntAc porphyra, purple. 
' From Latin /»m/jr, -icit, cinder. 
18 



said to be tilted up, as R ; when so much inclined 
as to be straight up and down, they are said to be 
perpendicular, or to stand on edge. When inclined 

1 From latin/oNum, a. leaf. 



GEOLOGY. 



rocks come to the surface, they are said to crop 
cut, and the exposed edge is therefore termed the 
■outcrop, as M ; the angle at which they are inclined 
is called the dip of the rocks, and is measured by 
the number of degrees from the horizontal in any 
direction, as 60° S. ; and the line of the outcrop 
along the surface is termed the strike or line of 
strike, because it strikes or runs across the country. 
When the strata are not straight, they are said to 
be bent or curved; and when greatly bent, twisted 
■or contorted, as P. When all the strata in a series 
lie at the same angle, they are called conformable; 
when at different angles, unconformable, as at A. 
Sometimes certain strata seem to have slipped down 
or to have moved up, so that rocks that should be 
opposite to one another are not so. The portion 
•that has slipped is naturally termed a slip, as C ; 
•that which has been heaved up, an upheaval or 
'hitch : where the strata at the slip lie at different 
angles, the slip is called a fault, as O. All such 
displacements of strata are known as dislocations, 
and they are much more frequent than the regular 
disposition of rocks on the surface of the earth. 
Below is a good example of such dislocations in 
coal strata, where they are abundant. The slips are 
marked dj a dike, of trap, e; a, b, c, shew the strata 
that have been torn upj the dark bars are coal 
-seams. When strata are bent in wavelike undula- 




Dislocations of Coal Strata. 

tions, they are said to roll, as H ; and the hollow 
or concave portions are termed troughs or basins, 
and the elevated portions ridges, as I and K. 

2. Unstratified Rocks. — These rocks are thrown 
up amidst the stratified, and assume different 
positions according to the manner of their up- 
heaval Where they throw the strata into various 
angles, the rock upheaved is termed the dis- 
rupting mass, as V ; at other times, they overlie 
the other rocks, and are then called overlying, as 
E ; they are also interjected between the other 
strata, and are said to be interstratified, as F. 
Sometimes they intersect the other strata by 
masses like walls, which are called dikes, as G ; 
and sometimes the disrupting mass breaks into 
branches, which are called veins, as N. 

When a broad face of rock is exposed, and the 
different rocks shewn, as in a cliff on the sea- 
shore, a railway-cutting, or a quarry, such ex- 
hibitions of strata are called sections; and these 
may be delineated on paper. Sections of the 
underlying rocks may also be made, by examining 
the different rocks in a country, though no section 
be exposed in nature. 

THE CONTENTS OF THE ROCKS. 

The contents of the rocks receive the general 
name oi fossils, from the "LaXinfossus, dug, because 
they require generally to be dug out of the earth. 



Fossils may be divided into two great classes 
animals and plants. * 

Fossil Animali. — In the rocks we discover spe- 
cimens of every class included in the animal king- 
dom. We find corals of all kinds, and of the most 
beautiful structure, some branched like some of 
the corals of the present seas, others standing in 
masses on the very spots where they lived and 
died, their remains giving beauty to our finest 
marbles. We see star-like creatures of all kinds, 
either spreading abroad their arms or curled up 
at rest, as they may be seen any day during the 
ebb of tide. Shells of every form, size, and colour 
meet us at every step, as distinct as we now find 
them on the shore ; and some formations, of vast 
thickness and extent, are formed entirely of the 
habitations of these little creatures. We may also 
gather crustaceans, such as the crab and the lob- 
ster, the minutest parts of their structure being 
perfectly preserved. We discover fishes of every 
kind and size, sometimes entire, as they fell to the 
bottom at death, or crushed and broken in the 
convulsions to which the rocks have been sub- 
jected. We can gather the hard scales, that 
defended them like armour ; can form collections 
of their teeth, their fins, their jaws, and their eggs ; 
and can construct them again as they swam about 
in the ancient seas. Insects, too, we can gather 
of every kind, and can see them as they flew about 
in the old forests, and got entangled in the resin of 
the great old trees. Birds, too, are found, though 
not so plentifully as other creatures, as, from their 
manner of life, they were not so easily carried 
down by rivers, and deposited in the mud at their 
mouths. We find reptiles of immense size, croco- 
diles, and lizards, and flying dragons, with their 
terrible teeth, sweeping tails, and adamantine 
hides. We come upon beasts of every size, from 
little creatures that burrow in the ground, to 
gigantic deer, elephants, rhinoceroses, and mam- 
moths; and may enter the very dens in which 
lived beasts of prey, and to which they bore their 
captured victims. 

These creatures differ more or less from those 
that now inhabit the globe, but they are members 
of the same classes ; and catalogues of them have 
been formed as of those of the present day. A 
visit to a museum in which fossils are exhibited 
astonishes every one with the multitude, variety, 
and beauty of those fossil creatures, and especially 
with the wonderful preservation of organisms the 
most delicate and frail. 

Fossil Plants.— But the vegetable kingdom is 
as fully represented in the rocks as the animaL 
We find trees of the most varied kinds, with their 
roots, stems, branches, leaves, flowers, and fruit. 
We can look with wonder on the exquisite carving 
on the stems of mighty trunks, hundreds of feet in 
height, that once formed forests as dense and im- 
penetrable as those of the Amazon. But more, 
we can behold the trees standing on the very 
places in which they grew and waved their great 
branches, and can trace their roots as they pene- 
trate the soil beneath. We can also gather plants 
of all kinds— reeds, mosses, rushes, sea- weeds, and 
beautiful ferns — preserved entire, and spread out 
on the rock as delicate and perfect as in the finest 
herbarium. These fossil plants have, like the 
fossil animals, been examined and classified by 
botanists, and we possess elaborate volumes on 
the botany of the remote ages when these plants 

' 19 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



grew, similar to those on the existing flora of 
our globe. 

Traces of Natural Operations. — But the rocks 
bear traces of more than all this. On them, we 
can see the very dints of the rain-drops of these 
bygone ages, and can calculate the direction and 
force of the showers that impressed them. We 
can walk over the rippled sands of the old seas, 
just as we can do over those we played on in 
childhood. We can also look on the footprints of 

f>rimeval birds, as they stalked in the mud of their 
ake or river homes; or gaze with astonishment 
on the great footprints, as large as a man's hand, 
of the huge reptiles that waddled among the reeds 
by the great old rivers. We can look into the 
craters of extinct volcanoes, can follow the flow of 
the destructive lava, and can gather the ashes that 
once illuminated the darkened heavens. We can 
trace the sources of ancient rivers, and dig in the 
mud brought down from their mountain sources ; 
can draw maps of the continents and seas as they 
existed thousands of ages past; can tell where 
great ocean-currents flowed, bearing huge icebergs, 
that grated the sea-bottom, and left their indelible 
traces on the granite and trap of our present hills ; 
and can shew where mighty glaciers once existed 
in valleys now famed for their beauty, where the 
genial sun sheds its warmest rays. In short, 
every element in nature, whether of air, river, or 
ocean, has left its deepest traces on the solid crust 
of our globe. 

AGENCIES IN THE FORMATION OF ROCKS; 

Any explanation of the manner in which rocks 
have been formed must account for all the 
phenomena, equally of composition, structure, ar- 
rangement, and contents. We must, for instance, 
explain how some rocks are stratified, and others 
not ; how some are horizontal, and others inclined ; 
and how plants and animals have come to be 
imbedded in them so far below the surface. Are 
there, therefore, any agencies engaged in the for- 
mation of rocks at the present time that produce 
effects the same in kind with these older masses } 
If we find that such exist, we shall have a key 
by which to interpret the rock-formations of the 
past. Let us consider, therefore, the Rock-forming 
Agents. 

Volcanic Agents. — The most obvious rock- 
formers at present in action are volcanoes. From 
circular openings, called craters^ from their cup- 
like shape, at the summits of these mountains, 
there issue forth at certain times great streams of 
molten lava, boiling water, red-hot fragments of 
rock, mingled with flames, and smoke, and steam, 
amidst confused and thundering sounds, and the 
general convulsion of the surrounding country. 
These lava-streams, increased by ashes and other 
substances, are often of great thickness, sufficient 
to bury cities ; as Vesuvius once did Herculaneum 
and Pompeii, and Etna did Catania at its base, 
where the river of lava gradually rose round the 
walls, finally drowning the city in its burning 
flood, after it had flowed twenty-four miles ! Suc- 
cessive accumulations of such outbursts deposit 
immense masses of rock, in the course of ages, 
round the centre of eruption; so great, indeed, 
that the larger portions of such mountains — and 

I Gredc eraOr, a cap. 



some of those in America are five miles in height 
— are formed of the successive accumulations of 
the crater itself. The molten lava assumes various- 
appearances after it has lost its heat : under water^ 
it remains hard and compact; in the open air, it 
becomes porous and cindery ; and in certain cases,, 
it assumes a columnar form. All around, lie light 
pumice-stone, slag-like masses, fine pulverised 
dust, and huge calcined blocks. Now, the Un- 
stratified rocks resemble in every feature these- 
volcanic discharges. We meet with the compact 
lava in our trap and greenstone ; with the cinder, 
in the lighter porous rocks ; with the ash, in our 
trap-tufis ; and with the columnar, in the basalt 
In exposed sections, we see the very vent through 
which these masses burst and overflowed the 
strata above ; and can trace the boundaries of 
the ancient molten streams in the cliffs and hills 
that everywhere vary the surface of the country. 
We can also see hardening and crystallising 
changes produced on the surrounding strata 
wherever the heat of the erupted matter pene- 
trated. We have therefore found the explanation 
of one great class of the rock-formations, the^ 
Unstratified, in the volcanoes scattered over the 
globe, that are at this moment depositing masses 
similar in kind to those that issued from the 
bowels of the earth in bygone ages. These unstra- 
tified rocks, therefore, are termed igneous} fronv 
being produced by firej volcanic, from having 
issued from volcanoes; and eruptive, from being 
produced by eruptions. 

Aqueous Agents. — Rivers, as they flow over 
their channels, gather accumulations of mud, sand,. 
gravel, and animal and vegetable remains, accord- 
ing to the size of the stream and the character of 
the country through which they pass ; and these 
they deposit at their mouths in seas or lakes. 
Sometimes the amount of ddbris thus deposited is 
so great as to form large tracts of land, as at the 
protruding mouths of the Ganges, Nile, or Mis- 
sissippi. Even in historic times, the land thus 
gained is of great extent. For example, at the 
mouth of the Po, a minor stream, the town Adria, 
which gave its name to the Adriatic Gulf from its 
extensive commerce in Roman times, is now nine- 
miles from the sea ! The mass of matter held in 
solution or borne along by the running water, 
sinks to the bottom when it reaches the sea, in a 
certain order. First, the heavier masses are de- 
posited, such as boulders and gravel ; then, the 
sand ; and last, the mud. Mingled with these are 
various animal and vegetable remains that have- 
been washed into the stream. Thus, every river- 
mouth presents an ever-growing series of beds of 
varying thickness and material, superposed the 
one on the other, and enclosing various remains of 
animal and vegetable life. These deposits would, 
in the above order, be converted, by pressure, into- 
conglomerate, sandstone, slate, shale, and coaL 
Thus, again, we have found a beautiful and per- 
fect explanation of the Stratified rocks as they are 
presented everywhere, by which their composition, 
stratification, and contents are fully accounted for. 
Stratified rocks, therefore, obtain the various 
names of sedimentary, because formed of the sedi- 
ment of rivers ; and aqueous^ because deposited 
under water. 

Organic Agents. — But animal and vegetable 



I From Latin igitit, fire. 



< From Latin a^tia, water. 



GEOLOGY. 



life is also busy in the formation of rocks. Away 
in the warmer seas of the Pacific, lives the coral 
insect or zoophyte, the skeletons of which compose 
the remarkable coral reefs that form the chief part 
of the numerous isles that stud that greatest of 
•seas. These reefs extend thousands of miles, in 
broad barriers, over which the wild waves dash, 
•or in detached groups that gradually gather mate- 
rial round them, and form new islands. In the 
rocks, we also find the remains of like corals, 
standing where they grew, or drifted away, and 
appearing as extensive formations of limestone. 

Again, the bottom of the sea is covered with 
.accumulations of minute shell-fish, of great depth 
and extending over wide areas, as is proved every 
day by soundings with the lead. The old rocks 
also exhibit strata identical in composition with 
these microscopic shells ; some limestones and 
■chalks, for example, being composed of millions to 
the square inch of perfect bivalve shells. Again, 
■the sea-bottom contains beds of shell-fish, of differ- 
•<nt kinds, and of great extent and thickness. 
If these were to die, and be subjected to sufficient 
•pressure, they would form a rock, exactly like the 
shell limestones so common in our rock- formations, 
and so valuable in agriculture and building. 

Then we possess the remains of ancient forests 
'in our great mosses ; and luxuriant growths of 
■swampy plants and impenetrable jungles in the 
mud islands of the deltas of our great rivers in the 
tropics. These, submerged and acted on by heat 
and pressure for ages, would become coal, similar 
to what we daily use for fueL Thus, organic life 
•of all kinds is everywhere busy in forming rock- 
masses, similar in character and appearance to 
those presented to our investigation in limestone, 
-chalk, and coal 

AGENCIES IN THE ALTERATION OF ROCKS. 

Disturbing Agents.— Stratified rocks in their 
"natural state would be more or less horizontal and 
•continuous. How, then, are we to account for the 
tiltings, upheavals, faults, and various dislocations 
so prevalent among the strata? Igneous forces 
furnish the solution. The whole globe is subject 
to convulsive movements produced by internal 
forces, which are seen in earthquakes, and by 
which the ground is torn into fissures, and the 
solid crust made to move in mighty undulations, 
that destroy and swallow great cities. Extensive 
tracts are also sometimes suddenly raised or 
•depressed. Sometimes, too, great yawning craters 
•open where previously volcanic movement was 
unknown, and continue for a time in active erup- 
tion. In these upheavals and subsidences, sudden 
•or gradual, of extensive tracts, we see the causes 
-at work of the dislocations of the rocks of former 
times, and of the elevations and depressions that 
•occurred throughout the geologic eras. 

Again, we know that in order to the deposition 
of strata of any thickness, the sea-bottom must 
have gradually subsided : does any such gradual 
subsidence take place at the present time ? It is 
ascertained, from extended observations, that on 
the northern shores of the Baltic, for instance, 
there has been a gradual rise at the rate of 4 feet 
in a century ; and, in South America, a rise of 85 
feet during the human period, at Valparaiso, 
•of 19 feet in 220 years ; while over all the world, 
and even round our own coasts, ancient sea- 



beaches may be seen at various elevations, mark- 
mg former sea-levels. On the other hand, the 
south coast of Sweden, the coast of Greenland 
over 600 miles, and parts of South America for 
the last 300 years, have been slowly sinking ; nor 
are the British shores free from such oscillations. 

Thus, again, we see that existing causes perfectly 
explain the gradual subsidences and upheavals 
necessary to the formation of the rocks and to 
their subsequent elevation into dry land. 

Disintegrating Agents.— Every stratified 
rock in the immense thickness of the crust of the 
globe has been formed of the debris of pre-existing 
formations, that have been ground down and held 
in suspension till deposited in the layers after- 
wards hardened into rock. Whence, then, this 
immense accumulation of matter, and what the 
disintegrating agents ? 

I. Atmospheric Agency.— The atmosphere, by 
its chemical action, and by the combined effects 
of alternate heat and cold, wetness and dryness, is 
continually crumbling down all exposed surfaces, 
forming new soil, and thus increasing the earthy 
covering of the globe. The wind, also, has an 
incredible power of drifting and heaping up sand- 
hills along the shore — as in the county of Elgin, 
where an ancient barony has been entirely reduced 
to a desert through this means — and of raising 
the waves of the sea, and wearing the rocks 
through the mighty force of its swooping billows. 
Frost, too, is one of the quietest but most powerful 
disintegrating agents; for when water has per- 
colated a mass of rock, the act of freezing exerts 
a great expansive force, which cracks the rock. 
But frost can work on a grander scale, for to its 
agency is due the existence of avalanches, glaciers, 
and icebergs ; which, whether sweeping with 
overwhelming convulsion, or crawling down the 
mountain side, or floating and grating on the ocean 
floor, continually and with terrible effect, wear 
down or dash to pieces every rock that obstructs 
their irresistible course. 

2. Aqueous Agency. — The most extensive aque- 
ous agent is rain, which wears, softens, percolates, 
and gradually wastes away the rocks on which 
it falls. Rain-water also gathers under the 
ground in large cavities, where springs are formed, 
which dissolve the interior rocks, and, bursting 
out, deposit their solutions of lime, iron, sulphur, 
soda, flint, and bitumen. One of the most power- 
ful degrading agents is, of course, the sea, which, 
as it beats on its rocky shores, wears, rolls, 
and grinds to powdery sand the flintiest rocks, 
and presents, as monuments of its mighty power 
of waste, those lofty cliffs that guard its shores. 
But more powerful, but less obvious agents of 
destruction than the sea, are seen in the many 
streams that everywhere traverse the land on their 
way to this boundless reservoir. The power of 
rivers in excavating and wearing away the surface 
of the globe, is much greater than at first thought 
might be supposed. Most river-valleys, however 
deep, have been mainly worn down by river-action, 
extending over immense periods of time. When 
we contemplate the mighty valleys, inclosed by 
towering peaks capped with eternal snows, that lie 
hid amidst the mountain solitudes of the Alps, the 
Andes, or the Himalaya, we may well be aston- 
ished at such a statement But that these huge 
excavations have been mainly produced by the 
combined action of air, frost, rain, and river, has 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



been demonstrated beyond a doubt by a vast 
accumulation of facts and reasonings on phenom- 
ena in all parts of the globe. Hence, valleys 
thus excavated are termed valleys of erosion^ from 
being ground out by the powerful action of these 
mighty agents. This being proved to be the case 
even during the human period, we have little 
difficulty in accounting for the great denudation 
everywhere seen, and for the immense accumula- 
tions of sedimentary matter that forms so much of 
the solid crust of our globe. 

Transporting Agents. — We have also to 
account for the deposition of strata in one part of 
the country, the materials for which have been 
obtained at great distances ; and for the transport 
of immense boulders hundreds of miles from their 
original seats, as exhibited in all parts of the 
globe. 

1. Aqueous Agency. — The most obvious agents 
of transport are rivers, that bear down from every 
part of their courses the debris deposited at their 
mouths. Their power of carrying masses of the 
heaviest materials is immense, as may be seen 
after a flood in the smallest streams in our neigh- 
bourhood. Waves have also a wonderful power 
in removing and carrying to a distance the blocks 
on which they daily dash. But the currents that 
flow through the ocean, which are but mighty 
ocean rivers, have the greatest power in this 
respect. By their means, materials of all kinds, 
organic and inorganic, are conveyed to incredible 
distances. The Gulf Stream, for instance, conveys 
substances from the South African coasts to those 
of Nonvay and the far north. 

2. Ice Agency. — But the transporting influ- 
ence of these currents in bearing rock-masses 
is greatest when icebergs are carried on their sur- 
face. These huge frost -mountains have imbedded 
in their mass huge blocks, which are gradu- 
ally dropped over wide areas as the ice slowly 
melts away. The size and number of some of 
these transported rocks are often almost incred- 
ible. Every country exhibits such travelled rocks, 
which are called erratic^ boulders ; and our own 
little island presents no mean examples of such 
ice-borne masses. 

But ice also acts as a transporter in the form of 
glaciers — those great ice-rivers that fill the upland 
valleys of the Alps, Himalaya, and other mountain 
systems. In front of every glacier, along its sides, 
and on its surface, are great collections of rocky 
fragments of every size, borne down by the ice- 
stream, and left as evidences of its existence when 
the glacier has melted away. Such collections of 
rocks are called moraines? from their mural or 
wall-like aspect as seen running across a valley. 
The distance to which such blocks are borne is 
astonishing, and depends on the size of the 
glacier. Evidences of extinct glaciers are seen in 
most countries, and we may trace their remains 
in our own island, where now not a particle of 
glacier ice can exist 

3. Igneous Agency. — It is evident that volcanoes 
have a great power in throwing out masses of 
different materials to great distances, and of carry- 
ing many substances on their mighty lava-streams ; 
and evidences of their power in this respect in 
geologic times are everywhere apparent Some- 

> From Latin e, out, away, and redo, rosum, to gnaw. 
' From Latin erro, to wander. 
' From Latin murus, a wall. 
32 



times the fine ashes that issue from the crater are 
borne by the wind to g^eat distances, often fifty or 
a hundred miles, where they are deposited as a 
layer of finest dust ; and this may account for the 
existence of trap-tuffs in places where no volcanic 
eruption seems to have taken place. 

Transforming Agents.— Rocks have also- 
undergone great changes in structure, character, 
and hardness from the state in which they were 
originally deposited. Thus limestone has become 
marble ; sandstone, quartzite ; coal, anthracite. 
Such change is known as metamorphistn,^ and. 
the rocks so changed are called melamorphic. 
The chief agencies producing such remarkable 
transformations are these : 

I. Pressure. — The effect of pressure is at once 
apparent when we reflect that by it chiefly the 
loose materials of rocks have been made to com- 
bine and form solid strata — as sandstone from 
sand, coal from vegetable remains. But pressure 
exercises a much greater influence than would at 
first sight appear. For example, the melting- 
point of substances is greatly affected by pressure,, 
some substances melting with much less heat 
under pressure than without it, others requiring^, 
more. The metamorphosing power of heat is 
greatly affected by pressure. Thus chalk, by heat,, 
becomes lime in the open air ; but under pressure 
fuses and becomes marble. Pressure is one cause,, 
and may be the chief cause of cleavage in slates : 
this is one theory, known as the mechanical ;. 
the other being that of heat, and known as the 
crystalline. 

2. Chemical Action. — This is one of the most 
secret, but one of the most general, transforming- 
agencies, and its influence can only be indicated 
here. By it, substances are held in solution, or 
precipitated; new substances are formed; rocks 
become entirely changed through the chemical 
affinities between their contents, or by being perme- 
ated by streams and waters bearing other soluble 
substances; the different materials in rocks be- 
come aggregated, and form layers or masses : in 
short, it manifests itself by countless secret and 
potent effects. 

3. Heat. — The greatest metamorphic agency is- 
heat, whether general or local. By it rocks are 
wholly or partially fused, and undergo rearrange- 
ment of their component crystals, and thus become 
changed in form and structure ; or they are sub- 
jected to partial change of all degrees of intensity. 
The influence of heat is always seen more or less 
near igneous rocks, and the eye can follow the 
change from the natural rock, and note the gradual 
increase of metamorphism as it approaches the 
igneous seat. By heat the most varied transforma- 
tions have been effected. Thus limestone and 
chalk have been changed into marble, schists into 
jasper and granite, sandstone into quartzite and 
hornstone, shales into flint and jasper, clay into 
Lydian stone, &c. But whole systems of rock 
have also been affected by heat, which are known 
as the metamorphic or crystalline systems. The 
chief metamorphic rocks are gneiss, quartzite, 
mica-schist, with hornblende and chlorite schists, 
clay-slate, and metamorphic limestone. These 
were originally sedimentary rock, with fossils ; but 
the metamorphism has more or less obliterated 
the lines of deposit, and more or less destroyed 



From Greek meta, change, and morphi, form. 



i^ 



GEOLOGY. 



their organisms. Hence they are characterised 
by great absence of fossils. 

Gneiss,^ so named from its thin layers, is a hard 
crystalline rock, in extremely thin bands, often 
twisted in a remarkable manner, and consists 
mainly of the same materials as granite. Quartzite 
is a metamorphosed sandstone, and is so called 
from its quartzy appearance, arising from the fusion 
of the sandstone. It must, however, be distin- 
guished from quartz itself. The schists are named 
from their chief ingredients. Clay-slate is that most 
useful rock which, when split up into thin layers, 
forms the familiar blue slates of our roofs, and 
the slate and slate-pencil of our schools. These 
rocks are often grouped together in nature, as in 
the Highlands of Scotland, where they form the 
mass of the mountains, and enter into the grand 
and beautiful scenery of that picturesque region. 
They occur most extensively in the older forma- 
tions, as the Laurentian, Cambrian, Silurian ; but 
it must be carefully noted that metamorphic rocks 
are found throughout all the geologic systems up 
to the Recent. For example, Carrara marble, 
which was long thought to be primary, is meta- 
morphic oolitic limestone ; and, in the Alps, ter- 
tiary strata have been so changed as to be with 
difficulty distinguished from the oldest rocks. 



It thus appears that the agencies now at work 
on our own globe are adequately sufficient to 
account for all the phenomena of the forming, 
disturbing, disintegrating, elevating, depressing, 
transporting, and transforming of the rock-masses 
that form the crust of the earth. Such being 
abundantly proved, and the laws of nature being 
imiform and unchangeable, we are not only 
warranted, but compelled, to infer that the same 
influences were at work in these bygone ages, and 
were the joint causes of the formation of our rock- 
systems as they are now presented to our eyes and 
subjected to our investigation. 

ROCKS AS RELATED TO TIME. 

The Length of Geological Periods, or Geological 
Time. — In studying geology, it is necessary to 
have an accurate notion regarding the nature of 
the periods spoken of. It is to be carefully noted 
that, in geology, time cannot be measured by years. 
When we examine any stratum of rock, with all 
its enclosed organisms, it is natural to inquire how 
long this mass of rock took to be deposited. We 
can judge of this only in the following way. From 
observation of river-action as at present exhibited, 
we see with what extreme slowness rock-masses 
are worn down into sand ; how a thousand years 
make an almost imperceptible change on a boulder, 
and even on the gravel by the shore. Yet we 
know that the sandstone before us, often hundreds 
«. of feet in thickness, is composed of grains of rock 
ground down by water- action, transported by 
rivers to the sea-bottom, and deposited there till 
other strata were heaped upon it ; and that in 
after-ages the grains united, and were hardened 
by pressure into the rock we see. What incal- 
culable ages, therefore, must this sandstone bed 
have taken to be thus formed! The more we 
think of these slow-working causes, the more are 

' From Anglo-Saxon gnidan, to rub. 



we astonished at the enormous periods of time 
that must have elapsed before the formation of even 
the thinnest layer of rock. Geological periods 
therefore, are quite indefinite in the matter o{ years. 
This inability to assert a definite number of years 
in regard to any formation, is no defect in the 
science, for the knowledge of this would add 
nothing to the conception we already have of the 
immense periods presented to our contemplation 
by geology. 

The Relative Ages of Rocks.— "^^x^xi we speak 

of the different ages of rocks, we can do so only by 

; comparison with others. Our ideas on this point 

j are merely relative. We can assert that one la>'er 

must have been formed before another; or that, 

I after its formation, and before the deposition of a 

^ certain other rock, a rise or fall in the strata took 

place; or that, at a certain point in the series, a 

volcanic eruption threw up a mass of igneous rock ; 

I and make like statements based on comparison of 

the rocks with one another. Our conceptions, 

therefore, regarding the connection in age between 

the various rock-formations are merely relative, 

! one rock being proved to have been formed before, 

or after, or during the formation of another. 

The Order of the Rock-formations. — By long- 
continued and widely extended observations in 
various parts of the globe, based on numberless 
data of composition, structure, inclination, and 
fossil contents, geologists have been able to form 
a definite list of the various rock-formations from 
the earliest to the most recent, arranged in the 
order of time. They have divided the whole of 
the rocks composing the crust of the earth into 
sections called 'systems,' and have subdivided 
these again into * groups,' in a certain well-defined 
order. So that when a rock is presented to their 
observation in any part of the globe, they can 
state, with more or less certainty, the system to 
which it belongs, and the period in the past history 
of the earth at which it was deposited. Regarding 
these rock-systems, one point is to be very strictly 
noted. Suppose that we represent the various 
rock-systems by the letters of the alphabet — the 
earliest by A, the second by B, and so onwards to 
the last and most recent, represented by Z. Now, 
the various rock-systems always stand in this rela- 
tive historic order ; so that the formation indicated 
by M comes after L, and before N, and cannot 
occur in any other relation to these two systems, 
wherever they may be found. At the same time, 
certain formations, one or more, may be wanting 
in some parts of the world, not having been 
deposited there ; so that one or more systems may 
not be represented in these districts. Thus, L and 
M may be absent. What two systems will then 
be found together? Certainly and unvaryingly, 
K and N. But here the historic order is not vio- 
lated, as it would be if N preceded K. The various 
rock-systems are, therefore, always presented in 
an unvarying succession in the order of their for- 
mation ; although, in different parts of the globe, 
certain strata, and even whole systems, may not 
be found. 

CLASSIFICATION OF THE ROCKS — 
THE ROCK-SYSTEMS. 

We now proceed to describe, in the order of 
their formation, the different kinds of rocks that 
compose the crust of the earth, and their fossil 

23 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



contents. As already said, geologists have divided 
all the rocks into different classes, according to 
their relative position and the fossils they contain. 
The whole of the stratified rocks are divided into 
eleven great systems, and each of these into sep- 
arate groups, to which names have been given, 
more or less descriptive of the strata to which they 
are applied. The systems have been named chiefly 
from localities in which they are largely or typi- 
cally developed, as the Laurentian ; in some cases 



from important rocks they contain, as the Carbon- 
iferous ; in others from their position or order, as 
the Recent. They are given tabularly below, with 
the reasons for the names, and their chief rocks, to 
give a definite idea and to assist the memory. This 
list should be carefully studied and comprehended 
before going farther. These systems are also 
grouped into three great Periods, and into two 
g^eat Cycles, according to the character and 
advance of the organic life they contain. 



R O C K - S y S T E M S. 



Systems. 


Reason of Name. 


Characteristic Rocks. 


Periods. 


Great Cycles. 


L Laurentian. 

IL Cambrian. 

IIL Silurian. 

IV. Devonian and Old Red 

Sandstone. 
V. Carboniferous. 
VL Permian. 


From the Si Lawrence in 

North America. 
From Cambria or North 

Wales. 
From Siluria or South 

Wales. 
From Devon and its red 

sandstone. 
From its coal strata. 
From Perm in Russia. 


EoziJon limestone 

and gneiss. 
Sandstone flags 

with fossils. 
Slates. 

Old red sandstone. 

Coal and iron. 
New red sand- 
stone. 


PALiEOZOIC ^. 

or Ancient Life 
Period. 


PALi«EOZOIC 

or Great Ancient Life 

Cycle. 


VII. Triassic. 
VIIL Oolitic or Jurassic. 
IX. Cretaceous or Chalk, 


From consisting of three 

groups. 
From its egg-grained rocks, 

and from Mount jfura. 
From its chalk rocks. 


Magnesian lime- 
stone, rock-salL 
Egg-grained rocks. 

Chalk and green- 
sand. 


Mesozoic « 

or Middle Life 

Period. 


Neozoic * 

or Great New Life 

Cycle. 


X. Tertiary. 
XL Quaternary or Recent. 


From being the third of the 
old geologic systems. 

From being the old fourth 
system, and from being 
recent. 


Clay and marL 
Peat and graveL 


Cainozoic^ 
or Recent 
Life Period. 



These systems we shall describe in order, be- 
ginning with the earliest, down to the most recent, 
gfiving the appearance and composition of the 
rocks, the uses to which they are applied, and the 
fossils they contain. We shall also endeavour to 
realise the state of the earth at each successive 
epoch, the scenery then exhibited, and the plants 
and animals that then enlivened the landscape. 
Below the Laurentian, another system is some- 
times given as existing, called the Metamorphic 
or Primary or Non-fossiliferous. It seems neces- 
sary to abandon this system. As shewn (p. 22), 
metamorphic rocks occur in all systems. The 
assertion of the absence of fossils is premature, 
and has always proved so in regard to other rocks, 
and is unscientific. The term primary is objec- 
tionable on like grounds. All existing rocks, as 
far as yet known, seem to be comprehended under 
the eleven systems given above, which we now 
proceed to describe. 

I.— LAURENTIAN SYSTEM. 

Description. — Immediately above the Non-fos- 
siliferous Metamorphic rocks lie the lowest of 
those that contain fossils. These have received 

1 From Greek palaios, ancient, and zion, an animaL 
• From Greek tnesos, middle, and zSon, an animal. 
3 From Greek caitws, recent, and zoon, an animal. 
< From Greek mos, new, and tdon., an animal. 
24 



the name of the Laurentian System, from their 
great development on the shores of the St Law- 
rence, in Canada. It was only quite lately, in the 
year 1863, that these rocks were grouped into a 
distinct system, from the discovery in them of 
certain fossil remains in Canada, having previously 
been reckoned metamorphic. The Laurentian 
System consists of certain schists, quartzose rocks, 
and limestones, all very highly crystallised — shew- 
ing good examples of metamorphic rocks. They 
form two groups, upper and lower. They contain 
no sandstones or shales, that occur so frequently 
in higher formations, such of these as once existed 
having been changed by heat. The limestones are 
very highly crystallised and metamorphosed, and 
of great thickness. The rocks, however, are all 
truly sedimentary, deposited under water, and 
have received their present aspect mainly through 
the agency of heat. They are found in Canada, 
Ireland, Norway, and Sweden, and, perhaps, in 
the north-west of Scotland. 

Organic Re?nains. — The discovery of the fossil 
remains that caused these rocks to be formed into 
a separate system, was made in Canada, and 
excited interest amongst geologists, because be- 
longing to a period when organic existence was 
thought impossible. The organism discovered 
received the name of the Canadian Eozdon^ or 

1 From Greek IBt, dawn, and tBoH, an animal. 



GEOLOGY. 



Dawn-animalcule, and consists of minute tubes 
or cells that are visible only under the microscope. 
Some still deny that this structure is organic, and 
regard it as merely a mineral appearance; but 
these are few. The general opinion now is, that 
here we have the earliest life-remains yet dis- 
covered on our globe ; and this is all the more cer- 
tain, that worm tracks and burrows were found 
in 1866 in the same formation. The discovery of 
these evidences of organic life, so long sought in 
vain, shews that more minute search may result 
in other remarkable discoveries, and that in all 
likelihood the name of Eozoon will be found to be 
premature. 

II. — CAMBRIAN SYSTEM. 

Description.— \mm&6.ia.\.e\y above the Laurentian, 
lies a series of slates, schists, and crystalline lime- 
stones, called the Cambrian System. It is so 
named from being first most fully described as it 
is found in North Wales, which in Roman times 
was called Cambria. The rocks in this series are 
less changed than the Laurentian, and therefore 
the remains in them are more numerous and better 
preserved. They are of great thickness, and are 
found in Wales, Cumberland, Ireland, North Ame- 
rica, and elsewhere. They are divided into two 
groups, upper and lower. Along with the older 
rocks beneath them, they everywhere form mighty, 
rugged, peaked mountains, like those of Wales ; 
and their worn, rugged aspect is due to their being 
so long subjected to wasting influences from their 
great antiquity. All these earlier rock-formations, 
from the Laurentian to the Silurian, are exceed- 
ingly rich in mineral wealth, most of the precious 
metals being obtained from them. Shooting 
through their hard crystaUine masses, we find 
veins of iron, copper, silver, and gold; and, from 
the presence of these metals, bare mountain tracts 
have teeming populations, where even the sheep 
with difficulty finds its scanty food. 

Organic Remains. — The fossil remains are all of 
the very lowest kinds of life. Sea-weeds and shells 
of different kinds have been discovered, and some 
■Crustacea — especially one that occurs abundantly 
in the next formation, called the trilobite. The 
tracks and burrows of worms, formed in the sand 
of the ancient seas, may also be seen perforating 
these hard masses. 

Scenery of Period. — During the Cambrian age, 
■quiet seas heaved their waters as now, tenanted 
with shells and crab-like creatures, while waves 
rolled on the sandy shores, over which worms 
■crawled, and into which they burrowed ; facts inter- 
esting as shewing that creatures had then the same 
Tcinds of habits as now, and that what we can see 
any day along our own shores, sends us back to 
the distant ages when the world was young. 

III. — SILURIAN SYSTEM. 

Description. — The Silurian System contains 
locks less changed by heat than those below, and 
•exhibiting more abundant life. In many of those 
already mentioned, the metamorphism has been 
so great as to render it difficult to say with cer- 
tainty how the rocks were originally formed, but 
henceforth all hesitation vanishes. They form 
two groups, Upper and Lower Silurian. They con- 
tain slaty sandstone, finely laminated, and often 



exhibiting ripple-marks ; conglomerates chiefly of 
rounded pebbles, clays, and limestones, with corals 
and other fossil remains, all of great thickness. 
The system has received the name of Silurian 
from being very fully developed in a part of South 
Wales anciently called Siluria} From these rocks 
are obtained roofing-slates, freestone for building, 
flagstones for paving and other purposes, lime- 
stones from which lime is got by burning, and 
valuable ores of lead, copper, silver, mercury, 
and gold. 

Organic Remains. — Parts of the stems and leaves 
of water-plants and club-mosses, and a few sea- 
weeds, are found, but all scarce and much broken. 
No land animals have yet been obtained, and 
though it would be rash to say that they do not 
exist, much seems to render this very prob- 
able. But marine fossils are numerous and well 
marked, some of them being very beautiful We 
find corals of different kinds, named according to 
their appearance, such as the sun, star, cup, pipe, 
chain, spider, and honeycomb corals. One of the 
commonest forms in the Silurian rocks is a very 
beautiful curved creature like the plume of a 
goose-quill, called the Graptolite^ from looking 
like a pen on the rockj some single, others double, 
some straight, others beautifully spiral. Another 
very abundant form is the Encrinite, a coral crea- 
ture more numerous in the Carboniferous System. 
We find also star-fishes, one beautiful and ' almost 
as uncompressed as if just washed up on the sea- 
beach,'^ and numerous fine shells with single and 
double valves, some, like the periwinkle and cockle, 
being abundant. But the creature that swarmed 
most in the ancient Silurian seas was the Trilobite,^ 
so called from its body consisting of three lobes or 
divisions, above which was set its head with large 





Oral [Astrea). 



Trilobite {Asa/kut de Buckii^. 
Silurian Fossils. 



double eyes, still to be found entire. It had various 
forms, and seems to have been very active, and 
was of all sizes, from mere specks to fine speci- 
mens ten or twelve feet long. Creatures like the 
scorpion, with toothed toes, are also obtained, and, 
in the upper beds, fishes interesting as the most 
ancient fossil-fish. 

Scetiery of Period.— Oi the dry land, we know 
little or nothing, except that it did exist, and 
nourished certain aquatic plants and club-mosses, 
whose remains were floated down into the great 
seas. But we can see mighty oceans, in which 
corals flourished, and encrinites waved their lily 
stems. Shells were abundant, and numerous crea- 
tures gambolled in the bright sun. These seas 
were fringed by sandy shores, on which worms 

1 Inhabited by the ancient tribe of the Silum- 

» From Gn^V graphs, I write, and lithos, a stone. 

» The Valaoittr asperinus. See Lyell's Studtnft EumtnU, 



p. 456. 
« From Greek treis, three, and Icbos, a lobe. 



SS 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



^ 



crawled and left their tracks ; gravelly beaches, 
that have become conglomerates ; and great beds 
of shells, that have given origin to thick lime- 
stones. Life gradually assumes more activity, and 
living forms become more numerous and elevated 
in the scale of existence, as we ascend in the 
system towards the active p>eriod that follows. 

IV.— DEVONIAN AND OLD RED SANDSTONE 
SYSTEM. 

Description. — This system of rocks has been 
rendereci famous through the writings of several 
geologists, especially the celebrated Hugh Miller, 
and is one that in itself possesses the very greatest 
interest. In early geology, the Coal-measures 
were considered very important ; and as both 
below and above them a great thickness of red 
sandstone is found, the rocks above were named 
the New Red Sandstone; while those below, being 
of course older, were called the Old Red Sandstone, 
or, shortly, the Old Red. This system consists of 
two types, the Fresh-water or Old Red, and the 
Marine or Devonian, so called from being exten- 
sively developed in Devonshire. These two types 
may not be of the same age, or if so, were de- 
posited under different conditions. The Old Red 
is largely developed in the centre and north of 
Scotland, especially in Forfarshire and Caithness, 
where it is extensively quarried, and in parts all 
over the world. The name ' Old Red ' indicates 
that the chief rock is a red sandstone, which is 
used very extensively for building. This also 
occurs in fine flags used for pavement, generally 
of a gfray colour, yielding the famous Arbroath 



and Caithness pavements. The remarkable roclc 
called Conglomerate or 'Plum-pudding Stone,' 
which looks as if it consisted of a consolidated 
sea-beach, is also extensively found at the base of 
the system. Like strata abroad coincide more 
with the Marine or Devonian than with the Old 
Red. They are found in many parts of the world,, 
and extensively with fine fossils in Russia and 
North America. Both types are divided into 
three groups — Lower, Middle, and Upper. 

Organic Remains. — There are fewer plant than 
animal remains found in this system. We find, 
sea-weeds of different kinds, marsh-plants like our 
bulrushes, sedges and horse-tails, tree-ferns and 
reeds, &c. Late discoveries have greatly increased 
the number of plants, so long thought to be so 
meagre, to above 2CX), rendering this system 
almost half as rich as the Coal-measures in this 
respect. Animal remains are numerous, varied, 
and beautiful. There are many species of corals 
and shells. The tracks of certain creatures, and 
deep burrows, sometimes eighteen inches deep 
and one and a half across, made by large burrow- 
ing worms, are frequently found. Many crusta- 
ceans are obtained, one of which is a huge kind 
of crab, sometimes six feet long, with terrible- 
looking toothed claws, called the Pterygotus^ or 
ear-wing. Reptiles are also found, two very large 
lizards being most frequent. 

But by far the most numerous specimens of 
ancient life are gigantic fishes. These creatures 
are all covered with hard bony scales, burnished 
with enamel, with fierce teeth, and great fins 
armed with long sharp spines, with which they 
defended themselves or attacked their enemies^ 






Cephalaspis,* or Shield-head. 



Coccosteus,* or Berry-bone. 
Old Red Sandstone Fishes. 



Pterichthys,* or Winged-fish. 



These fishes have received different names, ac- 
cording to peculiarities in their structure or 
appearance, and have been brilliantly described 
by Hugh Miller, who, when cutting the Old Red 
Sandstone as a mason, had his attention first 
drawn to geology by the brilliancy of their scaly 
armour. 

Scenery of Period. — The wide oceans in which 
the thin fine-grained flags were deposited must 
have been smooth and tranquil. Round the coral 
islands that rose in its gleaming waters coursed 
huge fierce fishes. The sandy shores became the 



coarser sandstone. Within tide-mark, numerous- 
great crabs lived, and caught their prey in their 
toothed claws ; shrimp-like creatures danced over 
the sands, and in them worms burrowed ; the 
waves ebbed and flowed, leaving their ripple-marks 
on the rocks we now see ; gravel beaches fringed 
the shore, where the surges rounded the pebbles 
and rolled the stones, helping to create our 

1 From Greek pteron, a wing, and ous, otos, the ear. 

* From Greek cephale, the head, and aspis, a shield. 

* From Greek coccos, a berry, and osteon, a bone. 

* From Greek pteron, a wing, and ichthys, a fish. 



GEOLOGY. 



I 



conglomerates; rain-showers fell, and left their 
impressions on the sandy bays pelted with their 
drops ; forests of sea-weed waved in the green 
waters and on the rocky reaches ; and shells 
adorned the rocks. Into the seas flowed great 
rivers, whose banks were fringed with reeds and 
flags ; ferns waved on the hill-side, tree-ferns 
reared aloft their feathery plumes, and broad- 
leaved plants clothed the surface of the landscape ; 
while large reptiles roamed through the forests, or 
crushed the reeds by the river-sides. 



V. — CARBONIFEROUS SYSTEM. 

Description. — Above the Devonian rocks lies a 
series of strata perhaps more generally known 
than any other, as they afford us what is so neces- 
sary to our comfort, the remarkable 
combustible stone called coal. They 
receive the name Carboniferous'^ from 
the fact that they contain coal, although 
they furnish many other important pro- 
ducts. These rocks are found in most 
regions of the globe ; but in none are 
they more fully developed, compared 
with the size of the country, than in the 
British Isles. They consist of sand- 
stones, limestones, shales, clays, iron- 
stone, and coal. The sandstone is of 
various qualities and colours, some of it 
very valuable and durable ; the beauti- 
ful stone of which the New Town of 
Edinburgh is built is from this system. 
The limestones are largely developed, 
and are of the greatest service for building and 
agriculture. The shales have of late become very 
valuable, as from them are distilled oils and other 
substances, including the celebrated parafifine oil 
and candles. The ironstone is of the 
very greatest value, and contributes very 
largely to England's wealth. 

It must not be thought that coal is 
found only in the Carboniferous rocks. 
Coal, being chiefly compressed vegetable 
matter, may be found in any rock-system 
in which plants are preserved. It is 
accordingly found in other systems, and 
often in great abundance. For example, 
the coal-fields of Virginia, some thirty 
or forty feet thick, belong to the Oolitic ; 
and coal of various kinds can be ob- 
tained, more or less, from most systems. 

The same is true of other products, 
such as limestone, sandstone, and iron, 
which last, though found in greatest 
abundance in this system, yet occurs 
in many others from the earliest. 

The Coal-strata are divided into three great 
groups— the Upper and Lower Measures, and a 
thick deposit of limestone, which separates them, 
known as the Mountain or Carboniferous Lime- 
stone. The Upper Coal-measures are also called 
the True Coal-measures, as they contain the great- 
est amount of workable coal; the Lower Coal- 
measures consist chiefly of sandstones and shales. 
The Mountain Limestone is so called because 
where it is most largely developed, as in York- 
shire, it rises into hills with great limestone cliffs. 

The industrial products of this system are 

1 From Latin carho, coal, axA/ero, to bear. 



nunierous and important. We find coal of alP 
kmds for household purposes and gas ; iron, sand- 
stone limestone, and fireclay. From the shales, 
are obtamed alum and the remarkable paraffine 
OIL bo abundant in America and elsewhere 
is this ancient oil, that when the earth is bored^ 
a flood of It issues forth yielding thousands o£ 
gallons daily, 

. Organic Remains.~'Y\,t organic remains found 
in this system are very abundant and remarkable. 
Plants are numerous, varied, and beautiful. Ferns, 
are found with the most perfect fronds, as dis- 
tinctly traced upon the rock as a modem dried 
fern on the pages of a book. We find also large 
and beautiful club-mosses exquisitely exhibited 
But the most luxuriant and beautiful of all are the 
great pme-like araucarias, the fruit' of which. 




Carboniferous Plants. 
Branch ai Asterophyllitesfoliosus, a kind of reed; 



a, 3, 4, Ferns. 



may, in some places, be gathered by the bushel ;. 
the tree-ferns, and tall reeds that grew in bound- 
less swamps and jungles along the banks of the- 
rivers, that swept in mighty volume to the carbon- 




v-f^^s^^y^y" 



Carboniferous Trees. 

Sigillaria ; 2. Stigmaria, root of Sigillaria, with rootlets attached, 
and pith ; 3. Calamite ; 4. Lepidodendron. 



iferous seas. We see the lepidodendron * or scaler 
tree, with its pine-like leaves, beautiful scaly 
bark, and great cones,^ from which the seed of 
the ancient pine may be gathered in hundreds to 
this very day; the sigillaria^ or seal-tree, witb 
its seal-stamped trunk and great pitted and 
branched root, called stigmaria^' long thought to- 
be a tree of a different species ; the calamite • or 

* Called TrigoHocarpum, from Greek treis, three, gonl, • 
comer, and carpos, fruit. 

* From Greek Upiss -idos, a scale, and dendron, a tree. 

* Called Upidostrobi, from Greek Upu, -ides, a scale, an* 
ttrobilos, a fir-cone. 

« From Latin sieilla, a seal. » From Latin ttiima, a mariu- 

* From Latin calamus, a reed. 

J7 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



reed, rising high into the air, like the bamboo, with 
its joints and leafy branchlets ; and many more 
equally beautiful and well preserved. 

The animal remains found are numerous and 
strange. Corals are abundant and beautiful. But 
no sea-creature was more common than the 
encrinite^ which rose on its long jointed lily-like 
stalk, and head with its hundred fingers, that 
moved on all sides to secure its prey, like the 
anemone of our own seas. The remains of 
€ncrinites are in some places so abundant as to 
form thick beds of limestone, called Encrinital 
Limestone ; and when these, hard as marble, are 
polished, they present a most beautiful surface, 
through which is seen the exquisite carving of the 
«ncrinite stars. The little joints of the stems are 
often found detached, with a hole through the 
centre ; these are known as Fairy Beads and as 
St Cuthbert's Beads ; and when strung together, 
■were used as a rosary, and no more beautiful 
ornament was ever hung round the neck of a 
saint. We also find star-fishes and sea-urchins ; 
and the spines of the latter may be seen running 
through the limestone like threads of burnished 
silver. The shells are very numerous and varied ; 
univalves and bivalves of both sea and land being 
everywhere found, and some of these can hardly 
be distinguished from shells gathered on our own 
shores, so perfect are they in form, colour, and 
structure. They may be detached from the rock, 
and collections made of them as easily as of 
modem shells. We find also crustaceans of 
different kinds ; and the last trilobites are found 
in the Coal-measures. Fishes are numerous and 
formidable, but less so than in the Old Red 
Period. Reptiles in both salt and fresh water 
have also left their remains, and their footprints 
may be seen on certain sandstones, as distinct as 
if made but yesterday on the soft mud. 

Scenery of Period. — In this remarkable period 
there stretched wide shallow seas, in which sported 
huge sharks, and whose waters washed the shores 
of many islands, guarded by great coral reefs, 
where the beautiful encrinite spread its waving 
arms. By the shores lived numerous shells, often 
in immense beds, that now form the mussel- 
band of the miner ; and into these seas flowed 
Amazonian rivers, bearing into the deep the spoils 
of their wooded and reedy shores. By their wide 
estuaries and along their banks lay extensive 
impassable swamps and jungles, in which gigantic 
reeds, calamites, and tree-ferns flourished in 
tropical luxuriance. Amidst these lurked fierce 
crocodiles and mighty lizards, which have left 
their footprints on the yielding mud. The whole 
surface of the land was covered with tall pines 
and tree-ferns ; the seal-palm, the scale-tree, and 
star-leaf shot into the air in impenetrable thickets, 
shaking their numerous cones in the breeze, while 
the hum of insects sounded through their still 
recesses. In the distance might be seen towering 
snow-peaks, and here and there the smoke of the 
volcano, the existence of which was felt in the 
xximierous earthquakes that shook the ground. 

V I. — P ERMIAN SYSTEM. 

Description. — Immediately above the Carbon- 
iferous strata, we find certain strata that used to 
be called, as already explained, the New Red 

* From Greek trinon, a lily. 



Sandstone, in contrast with the rocks below them, 
called the Old Red Sandstone. This New Red 
Sandstone series has been of late more thoroughly 
examined, and found to consist of two distinct 
portions, whose remains are so different that the 
series has been formed into two distinct systems, 
known as Permian and Triassic. The name 
Permian has been given to the system we now 
describe, from being developed very extensively 
in Perm, a province in the north-east of Russia. 
These rocks are found in many parts of the world, 
and largely in Scotland, England, Germany, and 
Russia. They consist of red and whitish sand- 
stones, shales, and limestones, containing much 
magnesia. The rocks are remarkably variegated 
in colour, so much so as to be called the Variegated 
System ; while the limestone receives the distinc- 
tive name of the Magnesian Limestone. As the 
old name suggests, the sandstone is of a reddish 
hue, and the two chief rocks, therefore, are the 
Red Sandstone and the Magnesian Limestone. 
The sandstones are used for building, as are also 
the limestones, which have been employed in the 
construction of the Houses of Parliament Copper 
is also extensively obtained from one of its shales 
in Germany, and also lead and zinc, but not very 
abundantly. 

Organic Remains. — The plants resemble greatly 
those of the Coal-measures. We find sea-weed, 
fine-leaved ferns, tall calamites and reeds, great 
pines with cones, tree-ferns, and palms like the 
modem fan-palm. The animal remains are not 
nearly so numerous as in the coal rocks. There 
are sponges, corals, sea-urchins, and beautiful 
shells. We also find fishes like those of the Coal- 
measures ; and the Permian is remarkable as the 
system where the ancient form of tail, in which 
the spine of the fish was continued into the upper 
lobe of the tail, becomes almost extinct, seldom to 
appear again. The reptiles of this system are 
numerous and perfectly developed, some of them 
being of gigantic form. Their footprints, in par- 
ticular, are remarkably abundant and large, and 
from these alone, the whole animal has been con- 
structed by learned men, the truth of their draw- 
ings being proved by subsequent discovery of the 
entire creature. Even pouched animals, like the 
kangaroo, are found in the American Permian, 
thus shewing a gradual but slow approach to 
modern life forms. 

Scenery of Period. — The Carboniferous Period 
was remarkable for the great activity of volcanic 
agents, but this period seems to have been com- 
paratively tranquil in this respect. The rivers 
carried in their waters much iron, as they did in 
the Old Red Period ; the seas appear to have 
been shallow, bearing in solution magnesia and 
salt, while animal and vegetable life seems scarce, 
as compared with other epochs. From the exist- 
ence of a rough conglomerate in the west of 
England, it has been argued that the greater 
part of the period was one of glacial action, 
with icebergs bearing blocks and rounded debris ; 
and if this was the case, we have a conclusive 
explanation of the scarcity of life during this 
period. 

V I I. — T RIASSIC SYSTEM. 

Description. — The upper part of the old system, 
known as the New Red Sandstone, has received. 



GEOLOGY. 



the name Triassic, which means triple, from 
being found in Germany in three distinct groups, 
of which the first and third alone exist in 
Britain. 

The system contains sandstones of different 
colours, shales, and conglomerates ; but the dis- 
tinguishing product is rock-salt. This occurs in 
beds of from seventy to one hundred feet thick in 
Cheshire, whence we obtain salt for daily con- 
sumption. Salt-springs also abound in salt dis- 
tricts, being formed by the issuing of water 
through the salt rocks below. The Triassic 
rocks are found in patches in the British 
Isles, but extensively on the continent of 
Europe and in America. 

Organic Remains. — The organic remains 
are very scanty, especially when compared 
with the exuberance of life in eras before 
and after. Plants are rare both in number 
and species. We find horse-tails, calamites, 
and ferns. The gigantic trees of the Coal- 
measures no longer exist, and we have 
instead short palm-like trees, like the modern 
cycas. The vegetation is mostly of a trop- 
ical kind. 

Animals are far from abundant, but are 
more numerous than the plants. We have 
no corals, and few encrinites, and bone- 
plated fishes are rare. There are a few 
shells, some crustaceans, and several great 
shark-like fishes. Reptiles, however, are 
numerous, and of gigantic size. One brute 
in particular, called the Labyritithodon^ from the 
labyrinth-\\V.t structure of a section of its teeth, is 
an uncouth, frog-like creature, with great staring 
eyes, and immense toothed jaws. The most 
abundant remains in the Triassic are the great 
footprints of large lizards. These are found in 
Scotland, but are so numerous in America, that 
above one hundred species of creatures have been 
distinguished, as indicated by these footprints. 
Huge birds, too, were numerous, and have also 
left their marks upon the rocks. These rocks 



VIIL—OOLITIC OR JURASSIC SYSTEM. 

Description. — ^We have now arrived at a 
remarkable epoch, whose remains, abundant and 
wonderful, have been more fully investigated and 
described by celebrated men than perhaps any 
other. The forms of life, habits, and scenery are 
more like those of our own times, and can there- 
fore be restored with the greater certainty. 

The term Oolitic is applied to a series of rocks 





Labyrinthodon. 

furnish the earliest evidences of warm-blooded 
mammals. 

Scenery. — The scenery of the old Triassic age 
seems to have been peculiar, and we can form but 
a dim notion regarding it. We can easily see that 
the seas were shallow, with bordering lagoons, in 
which the salt waterawere evaporated in the strong 
sun-rays, and left the salt-beds that are now of such 
service to us. By the muddy rivers lived great 
crocodiles, that lurked amid the reeds and pines, 
and fed on shell-fish and crustaceans, and left 
their footprints on the yielding mud ; while on the 
dry plains above, grew plants adapted for an arid 
soil and tropical climate. 

I From Greek labyrinthot, a labyrinth, and odout, cdcuUt, a 
tooth. 



Oolitic Plants : 
1, Palm; a, Tree-fern; 3, Cycas; 4, Pandaniis; 5, Zamia. 

which in England form three distinct groups— the 
Lias, Oolite Proper, and Wealden. 

The Lias is the oldest, and receives its name, a 
corruption of Hers or layers, from the thin varie- 
gated beds of which the rocks are composed, and 
which present a remarkable ribbon-like appear- 
ance not easily forgotten. The Oolite ^ is above 
the Lias, and is so called from the rock being 
greatly composed of small round grains like the 
eggs of the cod, so that it signifies the egg-rock. 
It is also called roe-stone and pea-stone, according 
to the size of the particles. These strange gran- 
ules consist almost entirely of lime or grains of 
sand coated with lime. The Wealden is the 
highest rock in the series, and receives its name 
from being developed largely in the Weald in 
Kent and Sussex. The name Oolitic has been 
applied to the whole system, because the egg- 
structure is common to all the rocks in the series ; 
the term Jurassic, from its being largely found in 
Mount Jura, is also given to it. 

The Oolitic system consists of a series of sand- 
stones, limestones (sometimes so hard as to be 
used as marble), shales, and clays, while ironstone 
bands, coal, lignite, and jet are abundant. The 
sandstones are useful as building-stone, the cele- 
brated Bath and Portland stones, so much used 
in London and the south of England, being 
varieties. The limestones are burned for agri- 
cultural purposes ; the clays are extensively devel- 
oped, and receive different names in different 
parts, and yield alum, sulphur, and fuller's-earth. 
Ironstone is abundant and good, and furnishes 
a great part of the iron of Yorkshire, being eleven 
feet thick. The coal is workable and abundant, 
which disproves the notion, too prevalent, that coal 
can be obtained only from the Coal-measures. 



> From Greek ion, an egg, and litkct, a stone. 



» 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




tignite is a less hard variety of coal ; and the jet, 
•which is only a crystallised coal, yields the beauti- 
•ful jet of Whitby, so much used for ornaments. 

Organic Remains. — The remains of plants and 
.animals are so abundant, that their enumera- 
'tion and description would fill volumes, and we 
-can merely roughly indicate some of their wonder- 
«ful forms. 

Vegetable life was abundant, requiring a warm 
•climate like that of Australia. We find sea- 
weeds, beautiful tree-ferns, lily-like leaves, palms 
flike the pandanus, and pines like the araucaria 
and yew. The clays that occur were the very 
•soil on which those ancient forests grew, and in 
-some of them, known as ' dirt-beds,' the roots are 
•seen in natural position, with part of the trunk 
troken over, while the tree itself lies close by, as 
if cut down by the woodman but yesterday. 

The animal remains are abundant and remark- 
able. We find sponges, exquisite star-corals, 
^beautiful encrinites, sea-urchins, worms, and lob- 
sters. The shells are very beautiful and varied, 
<he most remarkable being the ammonite, of which 
there are one hundred 
and thirty species, and 
the nautilus. Gigantic 
cuttle-fish flloated and 
spread their black ink 
through the oolitic seas. 
Fishes were numerous 
and large ; huge plated 
sharks devoured their 
prey, their very names 
telling terrible things, 
such as ' strong-tooth,' i 
'star-spine,'^ and 'great- 
jaw.' ^ Tortoises also 
floated on the summer 




Ammonite. 



But the most striking remains are those of 
reptiles, so numerous, strange, and uncouth, that 
the Oolite has been designated the 'Age of 
Reptiles.' We find enormous skeletons, some 
of them thirty feet long, of large lizards and 
-crocodiles, as of the Ichthyosaurus* or Fish-lizard, 
all being more or less strange and terrible. 

In these rocks, too, a most interesting discovery 
■has lately been made, that of the earliest feathered 
■creature — a real bird — in which the bones, claws, 
and full-spread plumage are finely seen. The 
remains of warm-blooded animals have also been 
ibund, especially of a kind of pouched creature 
like the kangaroo. 

Scenery.— i:\ie: scenery and animals of the Oolitic 
Period resemble, to a remarkable extent, those of 
Australia, both in vegetable and animal remains. 
The land and water went through many changes 
-during this long period. In the Lias times, the 
•seas were deep and tranquil ; under the Oolite, ex- 
.posed coral beaches were dashed by great breakers, 
that have left their work in broken shells and marls ; 
•while the Wealden seems to have been the carried 
-deposits laid down in the estuary of a mighty 
river, that rolled into the sea in what is now the 
south of England ; and the present icy lands of 
•the arctic regions were covered with the vegeta- 

' PycntfdHs, from Greek pycnos, strong, and odous, a tooth. 

* Asieracanihus, from Greek aster, a star, and acanthus, a 
«pine. 

^ Eugnathus, from Greek eu, well, and gnathot, a jaw or thorn. 

* From Greek ickthyt, a fish, and saures, a. lisird, 

30 



tion of a warm climate, which now appears as 
Oolitic coal strata. 



IX.— CHALK OR CRETACEOUS SYSTEM. 

Immediately above the Oolite lies a system in 
which the chief rock is the well-known substance 
chalk, and which has hence received the name of 
the Chalk, or, what is the same thing, Cretaceous^ 
System. In this system, other rocks also occur 
— namely, chalk-marl or blue clay, known by the 
local name of Gault or Golt; thick beds of green- 
coloured sand, called Greensand ; and, imbedded 
in the chalk, nodules of flint, which, when less 
pure, is called Chert j"^ and coal, in Vancouver's 
Island. The chalk is used for many purposes : 
when it is burned, it forms a useful lime ; when 
hard enough, is used for building-stone ; and 
when crystallised, forms a fine white marble. 
The flints are an important ingredient in china, 
porcelain, and glass, and from the sands we obtain 
fuUer's-earth. The whole system has been gener- 
ally divided into two groups, the upper being 
called the Chalk, and the lower the Greensand. 

Organic Remains. — The plant-remains are 
rare and imperfect, and seem to have been all 
drifted. Leaves of different kinds, palms, fruits, 
cones, and bits of pines have been discovered. 
Animal remains, however, are very numerous, 
and most beautifully preserved. We find sponges, 
corals, sea-urchins complete in form and struc- 
ture, beautiful star-fish, numerous crustaceans, 
and varieties of the lobster tribe. The shells are 
plentiful, and exquisitely beautiful in form and 
even in colouring, and are the finest fossil preser- 
vations found in any system. They include splen- 
did ammonites and nautiluses, and hundreds of 
other species, whose mere names would fill pages. 




Chalk Fossils. 



I, Plagiostoma spinosum; 2, Hamites intermedius; 3, Galerites 
albogalerus ; 4, Scaphites striatus ; 5, Belemnites mucronatus. 

Fishes are not numerous, but are well preserved, 
and, as in other systems, are named from peculi- 
arities in form or structure, such as the ' twisted- 
tooth,'3 the 'wrinkle-tooth,'* * thick-tooth,'^ and 
such like. Reptiles are also found similar to 
those in the Wealden. Bones of birds have been 
discovered, as also bones of what seems to be a 
species of monkey. 
Sceiury. ■ — The Chalk series appears to be 

1 From Latin creta, chalk. 

2 Irish ceirike, stone ; Welsh cellt, flint 

* Gyrodus, from Greek gyros, a twist, and odous, a tooth. 

* Ptychodus, from Greek /Ayr/jof, a wrinkle, and odous, a tooth. 

* Pycnodus, from Greek pycnos, thick, and odous, a tooth. 



GEOLOGY, 



■wholly a marine deposit. The land we know little 
'Or nothing of; sufficient, however, to shew that it 
was clothed with vegetable life, as in other periods, 
ibut little to picture its appearance. Over it, huge 
Wealden reptiles sought their prey, birds flew, 
:and great apes swung from tree to tree. But the 
ocean swarmed with varied life, mild sea-breezes 
"blew, and smiling sunbeams sparkled upon its 
waters ; for the climate was warm, as shewn by 
-the corals, reptiles, and monkeys. In the tepid 
waters lived numberless fishes and shells, and on 
their surface the nautilus spread its coloured sail 
The origin of chalk is a problem not yet satis- 
factorily settled, but the generally received opinion 
is, that the shores were fringed by coral reefs, 
which the dashing waves gradually wore down 
into fine powder, as they still do in tropical seas ; 
while millions of shell-fish teemed in its waters, 
and left their white shells as an impalpable sand, 
that, under the microscope, shews the tiny houses 
of the old inhabitants as perfect as on the day 
they died. Flint seems mostly to consist of concre- 
tions round sponges, corals, and other substances. 
It may be found at any epoch, and occurs in 
many other formations besides the Chalk, though 
<here in greatest abundance. 

X. — TERTIARY SYSTEM. 

We have now arrived at a new epoch in the 
liistory of the rocks, known as the Epoch of 
Recent Life. Henceforward, the plants and ani- 
mals bear not only a close resemblance to those 
now existing, but a great proportion of them are 
identical. We discover real exogenous trees, the 
same corals, crustaceans, and shells, equal-lobed 
fishes, birds, and mammaJs of existing families — 
and all these not only more numerous than 
hitherto, but also more perfectly preserved. The 
name given to this system is a relic of the names 
used in early geology, when all rocks were divided 
into Primary, Secondary, and Tertiary. In the 
Tertiary System, two great periods are easily 
distinguishable : i. The Warm Period; 2. The 
Cold Period. 

I. The Warm Tertiary Period. — This 
system exhibits clays, sands loose or hard, gypsum 
or plaster of Paris, and marls. The only true rock 
is limestone, made up of innumerable little shells, 
so numerous, that the rock is named, from its 
coin-\\\ie. shells, nummulitic,^ and is extensively 
found throughout the world. The limestone is 
burned for various purposes ; the clays are exten- 
sively used; the harder sands are employed for 
building ; and amber is also found. The strata 
occur exclusively in patches known as basins, 
the London and Paris basins being the most 
important. 

Fossil Remains. — The remains are both numer- 
ous and important. Of plants there are few 
marine specimens, as these seem to have been too 
tender to be preserved. We find, however, mosses, 
palms, ferns, leaves, fruits, seeds of different kinds, 
and whole pods of pea-plants. We have real 
exogenous timber, with specimens of palm, cypress, 
and fir. 

The animals resemble or are identical with 
existing species, and the Tertiary System has been 
-divided into periods according to the percentage 

1 From Latin nummus, a coin, and Greek Itthos, stone. 



of hfe-remains. We have corals, star-fish of the 
same species as those existing, and the shells are 
very beautiful, finely preserved, and scarcely dis- 
tmguishable from those to be gathered on our 
present shores. 

Among the fishes, we find various species of the 
shark, ray, sturgeon, sword-fish ; and of fresh- 
water kinds, the perch and the carp. Among the 
reptiles there are the crocodile and alligator, and 
the turtle. Birds are numerous, one specimen 
found in the Paris basin being gigantic Mam- 
mals are found of every existing order, amongst 
others, the whale, elk, stag, antelope, camel, llama, 
tapir, hog, rhinoceros, hippopotamus, beaver, hare, 
squirrel, monkey, elephant, horse, tiger, and hun- 
dreds of others. So numerous are these remains 
in some parts, that one rock in Norfolk is known 
as the Mammaliferous Crag. But the most 
remarkable of the ancient animals are the huge 
monsters whose skeletons, carefully reconstructed, 
may be seen in the British Museum, some of them 
above 10 feet high, and 20 feet long. The most 
wonderful is the mammoth, with two great tusks 
like an elephant. Others are the dinotherium ^ or 
* fierce beast,' the megatherium ^ or ' great beast,' 
and the mastodon.^ In different parts of the world, 
including many places in England, remarkable 
caves are found filled with bones of various ani- 
mals in clay or sands, known as ' bone-caves.' 
These caves have some of them been the dens of 
savage tigers and other brutes, the bones of their 
prey being still found; some have formed the 
abodes of different creatures at different times 
who have lived and died there ; while others have 
had their contents washed into them by floods. 

Scenery. — During this period shallow seas 
rolled under a genial sun, in which low islands 
rose crowned with palms, while the savage shark 
and sword-fish swam in the surrounding waters. 
The elephant ranged through the tall groves on 
shore ; the hippopotamus wallowed in the fresh- 
water lakes ; the rhinoceros crashed through rank 
jungles ; the mastodon, mammoth, and tapir trod 
in forests of palm ; and the wild ox and buffalo 
roamed over wide grassy prairies. 

2. The Cold Tertiary Period.— Immediately 
above the strata just described, with these strange 
organisms that speak of a warm climate, are found 
remarkable accumulations of sand, often found 
pure in hillocks ; gravel, and clay interspersed 
with rounded worn boulders, known under the gen- 
eral title of the 'Boulder-clay,' some of the boulders 
being of enormous size. From various phenom- 
ena, it has been proved that the climate became 
arctic in character, and our country and others 
were enveloped from shore to shore in a vast ice- 
sheet, like the Greenland of to-day. From the ends 
of this huge ice mantle, immense masses broke off 
and floated away as icebergs. By and by, how- 
ever, the climate became milder, and Britain looked 
like Norway and Iceland, with glaciers on the 
higher grounds, reaching here and there to the 
sea. Gradually the great ice-fields melted away 
under the rays of the genial sun, and our country 
looked like the present Switzerland, till at length 
the last glacier disappeared from the highest hills. 
The effects of all the wear and movement of these 

1 From Greek deituis, terrible, and ikfricn, beast. 
S From Greek megas, great, and tM/rioM, beast. 
» From Greek mas/as, a nipple, and odaus, odontot, m tOOtb. 
from nipple-like projections on its grinders. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



ice-masses, whether grinding down the land or 
grating on the floor of the ocean, or dashing 
against opposing islands, are seen in the thick 
clay and sand deposits everywhere around us, 
inclosing worn stones and gravel ; the scratched 
and rounded rock-surfaces, often bright and smooth 
as polished marble ; the 'erratic boulders,' perched 
on our hill-tops and plains ; and the general wavy 
outline of all higher ground throughout our land. 
This glaciation has been ascertained to extend 
over the whole of Northern Europe and America, 
and round the shores of the Antarctic Ocean. 



XL— QUATERNARY OR RECENT PERIOD. 

We have now reached the last of the great 
geological epochs, during which sea and land, 
plants and animals, were much the same as they 
are now. This last system has been variously 
named the Post-tertiary, Quaternary^ or Recent. 

The whole system may be divided into two chief 
periods : 

1. The Prehistoric^ or that before history was 
written. 

2. The Historic, or that since history was 
written. 

During the whole epoch, there is little or no 
solid rock, the whole deposits consisting of clay, 
sand, gravel, mud, peat, and the like. 

Oi prehistoric deposits, we find such remains as 
these : plants of all kinds, all common shells and 
corals, and common animals, with a few now 
extinct, such as the long-fronted ox, the gigantic 
Irish deer — a creature ten feet high to the top of 
its horns — the elephant, rhinoceros, hyena, bear, 
and mammoth, besides human remains in the shape 
of bones, canoes, ashes, dwellings, and weapons. 

In historical times, we find similar remains, but 
the deposits are comparatively small, and the 
plant and animal remains are almost solely those 
now existing in each country. Men have left 
traces of themselves in buildings, coins, imple- 
ments, weapons, and works of art. While peat- 
bogs have been formed, forests have been sub- 
merged or cut down, and considerable changes in 
sea-level have taken place. 

Since the Glacial Period, in the Tertiary, a series 
of changes has been going on without intermission, 

> From Latin fuaterHut, fourth, as coming after the Tertiary. 



accomplished by various causes and in various 
ways. The land has changed its level several 
times both by elevation and depression, the sea. 
thus alternately encroaching on and retiring from, 
the land. Whole countries have been gained 
from the ocean, such as the Fens in England and 
the greater part of Holland. Old beaches may be 
distinctly traced, with their cliffs, shores, and 
shells far above sea-level. Whole forests have 
been submerged, whose old trunks and fruits are 
thrown up by every storm. Huge accumula- 
tions of sand, blown or washed, have been found 
along its shores. Rivers have been depositing^ 
new matter under the ocean at their mouths,,, 
increasing the land by the formation of deltas,, 
sometimes hundreds of miles in extent, laying 
down fine carse-land along their banks, that now 
forms the richest soil of the farmer, and leaving 
terraces far above their present level, to mark 
their former beds. Many lakes have been formed, 
others have been gradually silting up from the 
earthy matter brought down by rivers, while some 
have become dry, their beds being now waving 
with corn. Animals have been busy forming new 
islands and continents, as in the Pacific, where 
the coral insect leaves its skeleton to form the 
nucleus of future islands. Igneous agencies have- 
been and are as active as in the olden times in 
changing the land and throwing out vast deposits 
of lava and ashes. 

Man. — It is an interesting question how far 
back man extends into these geologic eras, and 
this important inquiry has of late years received 
great attention. Striking results have also been 
arrived at. It seems to be indisputably proved 
that man existed as far back as the great Glacial 
Period, at the close of the Tertiary epoch, and 
that he was contemporary with the hairy rhi- 
noceros, mammoth, woolly elephants, and other 
gigantic creatures now long extinct, which he no 
doubt hunted, as he now does the fox and the 
deer ; at which period Britain was united to 
France, where now the sea flows in the Strait of 
Dover. But this inquiry is yet in its infancy,, 
and it would, therefore, be unwise to make posi- 
tive statements where our data are insufficient. 
Enough has, however, been discovered to shew 
that in our own quiet land men lived for many 
ages with strange denizens, and under conditions, 
very different from the present. 




Rocking Stone, Fall river. 



METEOROLOGY. 



METEOROLOGY explains the laws which 
regulate weather, seasons, and climates. 
It involves particularly the consideration of the 
atmosphere— its pressure; its moisture; the altera- 
tions made upon it by heat and cold ; and its 
electrical condition. It is by an accurate know- 
ledge of these that we are enabled to understand 
the nature and causes of the incessant movements 
and changes going on in the air around us, and 
of the ever-varying appearances of the sky over 
our head ; including the phenomena of winds and 
storms, of rain, dew, hail, snow, mists, and clouds, 
and their connections with one another, and with 
seasons and places. 

THE ATMOSPHERE. 

Its Composition — General Structure— Density — Pressure. 

The atmosphere is a vast ocean of invisible 
gaseous matter, enveloping the terraqueous globe, 
and extending to a considerable height. Although 
it cannot be seen by the eye, it is yet felt to be an 
inert, material mass, which resists bodies in their 
motion through it, and when set in motion itself, 
possesses momentum or impetus, like a flying ball 
or a running stream. Another property of the 
atmosphere, which proves its genuine materiality, 
is its weight or pressure. It presses upon the 
earth, exactly as the sea does, under the influence 
of gravitation. At the sea-level, the average pres- 
sure is I4f pounds on every square inch ; it is 
nearly the same as the pressure of a lake of 
water 33 feet deep, or a lake of mercury 2J feet 
deep. The construction of the barometer, or 
instrument for constantly measuring this weight, 
and shewing the degrees of its fluctuation from 
day to day, is explained under PNEUMATICS. 

The fluid of which the atmosphere consists, 
is found to be not a single substance, but a 
mixture of several substances, totally distinct in 
their properties, and serving quite different 
offices in the economy of nature. The two chief 
ingredients — nitrogen and oxygen — which make 
up more than Hths of the whole mass, are as 
different in their character as water and alcohol. 
The proportions of these two are very nearly 
77 of nitrogen to 23 of oxygen by weight. The 
nitrogen is therefore the principal element in 
point of quantity ; but the oxygen performs the 
greatest variety of functions : it is the supporter 
of life, and the indispensable agent in combustion, 
in putrefaction, and in many other natural pro- 
cesses. 

Deferring in the meantime the consideration of 
the other ingredients of the atmosphere, we have 
to study in the first place the mode of mixture of 
these two gases, and the general structure of the 
mass they compose. Although the mechanism 
and constitution of a gas are not apparent to our 
senses, yet we can infer with certainty that it is 
made up of atoms or molecules which keep one 
another at a distance by a repulsive force. From 
the fact that any gas can be compressed into a 
very small fraction of its ordinary bulk, we are 
sure that its particles are usually at a great distance 
3 



from each other in comparison with their size. 
Now, suppose two flasks connected by a tube 
having a stop-cock, by which communication can 
be cut off, and suppose the one filled with nitrogen, 
and the other empty; on turning the stop-cock, 
part of the nitrogen will rush into the empty flask 
until it is equally spread over the whole space ; 
for there is no stable balance of the repulsion 
if a particle is nearer its neighbour on one side 
than on the other. This uniform diffusion takes 
place almost instantaneously when the one flask 
is empty. But now, suppose both filled, the one 
with nitrogen, and the other with oxygen ; when 
the communication is opened, each gas spreads 
itself uniformly through the whole space of both 
flasks, precisely as the nitrogen alone did, only in 
this case time is required. The gases mutually 
interpenetrate, and the molecules of the one retard 
the progress of those of the other, but do not 
otherwise affect the ultimate result. Each gas is 
independent, and distributes itself, and exerts its 
pressure precisely as if the other were not there. 
It is owing to this important principle that the 
proportion of oxygen to nitrogen is the same in 
all parts of the world and at all heights. The same 
law of uniform diffusion, and independence of the 
presence of other gases, holds with regard to the 
carbonic acid gas and the aqueous vapour existing 
in the atmosphere, although, in the case of aqueous 
vapour, its constant liability to condensation 
prevents its ever attaining to a state of actual 
uniformity. 

Taking the entire mass of the atmosphere, con- 
sidered as an ocean of gaseous or elastic fluid, its 
density must diminish as we ascend from the 
earth. The rate at which the density of the air 
diminishes upward, and the estimation of its entire 
height, are complicated by the decrease of tem- 
perature that is found to take place as we ascend 
(see page 41). It may be stated here, in a general 
way, that one-half of its material mass lies within 
three miles from the earth, and three fourths of it 
within less than six miles. From the observation 
of luminous meteors, it is inferred that it is at 
least one hundred miles high, and that, in an 
extremely attenuated form, it may even reach tw» 
hundred miles. 

MOVEMENTS OF THE ATMOSPHERE. 

All the movements and changes to which the 
air is subject, originate, some way or other, in the 
unequal distribution of heat. 

If two adjoining spots of ground are of unequal 
temperature, and communicate an unequal tem- 
perature to the columns of air lying upon them, 
the column which is most heated will be expanded, 
so as to overtop the other, and will also be made 
rarer or lighter. Two effects will arise from this : 
a lateral or horizontal movement of the air from 
the cold to the warm column will take place beloWy 
according to the general law of hydrostatics, that 
a heavy fluid buoys up a light one. But if we 
consider the condition of the two columns above, 
or at their upper ends, wc will find that the 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



opposite effect must arise. Not only will the upper- 
most portion of the long column, which rises to a 
point where the short columh has ended, and has 
therefore nothing but a vacuum to flow to, have a 
side-movement towards the other, but portions far 
beneath the top ^will have a pressure so much 
greater than the contiguous portions of the shorter 
column, that they too will flow out laterally, and 
determine a current tending to equalise the differ- 
ence of heights and pressures. 

When a difference of temperature exists between 
two spots that lie near one another, the effect of 
the aerial currents which take place between 
them is to equalise the temperature. Its lateral 
currents are the effect of unequal heating, and in 
some measure the remedy. These lateral cur- 
rents are felt and recognised by us under the 
name of winds. If the differences of warmth that 
originate them were only limited and temporary, 
the carrying of heat to and fro would bring about 
an equality, and then the air would come to a 
perfect repose ; but these differences of warmth 
are perpetually kept up ; hence the lateral currents 
go on for ever without ceasing. The middle 
band of the earth, or the equatorial zone, is 
exposed to the burning radiance of a direct sun, 
while the two polar regions are so faintly heated, 
that snow never melts upon them ; and this great 
standing inequality keeps up two grand sets of 
movements, which encompass the globe. The 
equatorial air, being warmer and lighter below 
than the air on each side, is buoyed up by the 
cold masses moving in upon it from north and 
south, and thus two great under-currenls are 
maintained between the poles and the equator. 
The equatorial mass being expanded far upwards, 
•overtops and overpresses the upper portions of the 
colder columns on each side, and therefore flows 
in upon them on both sides ; thus causing two 
great up{>er-currents towards the poles, while the 
under-currents are moving from the poles. The 
inequality of the equatorial and polar regions in 
respect of heat is thus in some degree mitigated ; 
but it is by far too great to be entirely done away. 

We have supposed, for simplicity's sake, that 
the atmosphere is divided into an equatorial and 
two polar masses ; but in reality there is a con- 
stant gradation from the equator to the polar 
regions, and the movements will take place be- 
tween every two adjoining portions of atmosphere 
of which one is farther north or south than the 
•other. 

Although, as a general rule, the temperature of 
the earth decreases from the equator to the poles, 
this is not strictly or at all times true. Various 
causes occur to render a high latitude as warm 
as, or warmer than a lower, and in such a case a 
contradiction will arise to the general movement, 
which will have peculiar local consequences. 

VAPOUR OF THE ATMOSPHERE. 
Vaporisation— Dew— Mist— Qouds— Rain — Hail— Snow. 

Next in quantity to nitrogen and oxygen, 
although very small compared with these, is the 
vapour of the atmosphere ; that is to say, the 
gaseous water or steam that is constantly present 
in it. Although comparatively small in amount, 
this ingredient of the atmosphere is of immense 
importance in its effects. Unlike the other gases, 
it is easily reduced from the aerial to the liquid 

34 



form, or to water as we usually find it ; and it is 
constantly going through the processes of be- 
coming liquid and descending to the earth, and 
again rising into the air in the gaseous or in- 
visible form. The great agency connected with 
these transformations is heat. When water 

E asses into steam, it takes in a large amount of 
eat, which is rendered insensible to the feeling or 
to the thermometer ; and when steam or invisible 
vapour is condensed into water, all this heat is 
given out again (see Natural Philosophy). 

It is essential to bear in mind that true gaseous 
water, steam, or elastic vapour of water, which all 
mean the same thing, is invisible, like the other 
portions of the atmosphere ; and that the white 
cloud that appears at the chimneys of steam- 
boats and locomotives, and at the spout of a 
kettle, is not gas or elastic vapour, but vapour 
partially condensed, whose particles only require 
to be brought together to become drops of water. 
It is, in fact, water in the form of something like 
dust. Mist, fogs, and clouds are of the same 
character : they are not gaseous steam, but pre- 
cipitated watery particles destitute both of mutual 
repulsion and of the latent heat of steam. When 
the atmosphere contains nothing but true steam, 
it is transparent and cloudless. 

The formation of steam out of water is most 
conspicuous in the process of boiling, where the 
surface is kept in an intense bubbling state, each 
bubble containing a mass of steam, which forces 
its way up into the air. This boiling takes place 
at 212° of the thermometer, called for that reason 
the boiling-point. The steam thus formed has 
an elastic force equal to the pressure of the 
atmosphere, or a force of 14I pounds to the square 
inch. The reason for the violent escape of steam 
at 212° is, that it has attained a force equal to 
the weight of the atmosphere pressing on the 
water, and is therefore able to set aside this 
pressure, or make its way in spite of it. But 
even at temperatures below boiling, water passes 
into steam slowly and invisibly. It is well 
known that a wet surface soon becomes dry ; 
in other words, that the water upon it disap- 
pears. Water, however, cannot be annihilated ; 
in the drying process, the liquid water becomes 
gaseous invisible water or steam, and mixes with 
the other steam contained in the air. 

The rapidity of the process of drying up, or of 
the passing of water into steam, depends, in the 
first place, on the temperature of the water. We 
have seen that it is abundant and violent at 212° ; 
and it is less and less for every degree downwards. 
The elastic force of the steam produced also 
depends upon the temperature. The elastic force 
of steam at the boiling-point is equal to the 
pressure of the atmosphere ; while the elastic 
force of steam produced silently at 80° is only ^^"Ca. 
of the elasticity of the atmosphere, or equal to 
one inch of the barometer. 

Now, the entire quantity of steam that can rise 
is limited by the temperature in the same manner 
as the elasticity is limited. Water at 80° will give 
forth vapour, until as much has been produced in 
the atmosphere as would counterbalance one inch 
of mercury ; evaporation then ceases, and the air 
is said to be saturated with steam. Whether the 
steam rise freely into the atmosphere, or rise into 
a vacuum, no more will be produced at 80° than 
this quantity. If the temperature were raised to 



METEOROLOGY. 



90°, there would be the means of supporting an 
additional quantity of steam, and evaporation 
would again go on, until as much were distributed 
through the air as of itself would counterbalance 
I '36 inches of mercury, or about -ij^jd of the weight 
of the whole atmosphere. With every new ad- 
dition of heat, new evaporation would go on, 
which would be of the silent kind up to 212°, 
when the full pressure of the atmosphere would 
be reached. But as the water on the earth's 
surface does not rise much above 80° even at the 
equator, and is far below this temperature in 
other regions, the whole weight of vapour in the 
air rarely amounts to one inch of mercury ; so 
that, if the pressure due to nitrogen and oxygen 
by themselves were 29^ inches, the whole pres- 
sure, including the vapour, would be only about 30 
inches, and at the utmost 30^ inches. 

It has been stated, that at 80° vapour rises till 
as much exists in the air as weighs an inch of 
mercury ; and that if the heat be increased, an 
additional quantity can be produced and sup- 
ported. Let us now consider what must happen 
if the air were saturated with all that could be 
maintained at 80°, and if the temperature were 
then lowered, say to 60°. While at 80°, the 
vapour may amount to an inch ; at 60°, it 
amounts only to '$2, or little more than half an 
inch. If, therefore, the full quantity which can 
subsist at the higher temperature has been pro- 
duced, and if the temperature then descend to the 
lower point, there will be nearly half an inch too 
much for the reduced temperature, and this excess 
will be thrown out in the state of visible non- 
elastic vapour, or fall down as liquid drops. There 
will be either some kind of fog, cloud, or mist, or 
the aggregation of these into watery coherence. 

Tables have been formed, the result of accurate 
experiment, shewing the elasticity of the vapour 
that can be maintained at each degree of Fahren- 
heit, from 0° to 90°, expressed in inches of baro- 
metric pressure. 

If less steam is formed than could be sup- 
ported at the temperature, there is said to be a 
certain amount oi dryness or thirstiness in the air; 
meaning that there is room for further evaporation. 
If the quantity of vapour in the air is less than 
what is supportable at the temperature for the 
time being, there is some lower temperature which 
this quantity would completely saturate. Such 
temperature is called the temperature of the dew- 
point. The dew-point is the lowest point to 
which the air can be cooled down without giving 
out visible moisture. If the air were saturated, 
the temperature and the dew-point would be 
the same ; if the air is dry, or not saturated, 
the dew-point temperature is below the air tem- 
perature ; and the difference between the dew- 
point and the temperature of the air is a measure 
of the dryness. 

The number of degrees of Fahrenheit between 
the air temperature and the dew-point temperature 
is not, however, the exact estimate of the dryness, 
as will be seen from the following example. Sup- 
pose the temperature of the air 80°, and the dew- 
point 70°, then the amount of additional vapour 
that could be supported would be found thus : 

Vapour sustainable at 80°, l-ooi inches. 
» w 70% "727 inch. 

Difference, . . -274, above l-4th of inch. 



Thus a difference of 10° of temperature makes a 
vacancy for a fourth of an inch of vapour. Take 
now a difference of 10° farther down in the scale. 
Suppose the air 40°, and the dew-point 30° : 

Vapour sustainable at 40", -264 inch. 
" » 30', -ise . 

Difference, . . 078, about 1.12th of.inch. 
So that a difference of 10° between 70° and 80" 
makes a dryness or deficiency three times as great 
as a difference of 10° between 30° and 40°. Water 
would disappear three times as fast in the one 
case as in the other. 

As the mercurial column expresses only the pres- 
sure of the sum-total of the atmosphere, some other 
means must be adopted for finding the amount 
of vapour by itself. Instruments used for this end 
are called hygrometers ; from the Greek hygros^ 
moist, and metron, a measure. 

Apart from instruments, we judge of the dryness 
of the air, or of the additional amount of vapour 
which it could sustain, by the time required to dry 
wet bodies, such as the ground, or wet clothes 
hung in the air. 

The chief instruments for determining with 
accuracy the dryness of the air, and the actual 
amount of aqueous vapour that it contains — 
technically its hygrometric condition — are Daniell's 
hygrometer, and the wet-and-dry-bulb thermom- 
eters. 

The principle of Daniell's hygrometer is to cool 
the air down upon some surface till dew appear, 
and to mark the temperature when this happens. 
Thus, suppose a tumbler standing in the open air 
is cooled by pouring in cold water, or any other 
cold liquid, until the sides of the tumbler are 
covered with dew, the temperature of the glass at 
the moment that the dewing begins will be the 
temperature of the dew-point. In the actual 
instrument, the cooling is produced by the rapid 
evaporation of ether. But as the process of 
observation is rather delicate, and attended with 
trouble and expense, the wet-and-dry-bulb ther- 
mometers have come into more general use. 

The determination of the dew-point by the wet- 
and-dry-bulb thermometers depends on the effect 
of evaporation in causing cold. When water 
passes into invisible vapour or steam, it absorbs 
from whatever substances it touches a large 
amount of heat, and the more intense the evapora- 
tion, the greater will the cooling be. In applying 
this principle to measure the humidity con- 
tained in the air, two thermometers are taken 
— one of the ordinary construction, which serves 
simply to give the temperature of the air ; and 
the other having its bulb covered with a piece of 
rag, which is kept constantly wet by communi- 
cating with a cup of water by an absorbent wick. 
The water round the bulb will be constantly 
evaporating when there is any dryness in the air ; 
and the greater the dryness, the more intense the 
evaporation, and consequently the greater the cool- 
ing of the bulb. Hence this moist-bulb ther- 
mometer will fall in proportion to the dryness of 
the air at the time. We have therefore only to 
compare the two thermometers — the one giving 
the air's temperature, and the other a reduced 
temperature depending on the rate of evapora- 
tion or the degree of thirstiness — in order to 
judge of the comparative quantity of moisture ex- 
isting in the surrounding atmosphere. Tables 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



are used along with this hygrometer for calculating 
the dew-point temperature, which is ascertained, 
without calculation, by Daniell's instrument.* 

The force of evaporation, or the quantity of 
water which is converted into invisible vapour in 
a given time, depends upon the dryness of the 
air, and upon its stillness or motion. The effect 
of a current of air is to carry off the vapour from 
the surface as it rises, and leave the space free 
for an additional supply. The more rapid the 
wind, the faster every wet surface dries up. 

Clouds. — We must now consider more par- 
ticularly the peculiar forms of visible vapour. 
Mist, fog, and cloud are names for nearly the 
same thing. When there is a general haze of 
precipitated vapour covering the whole sky, and 
coming down to the surface of the earth, it is 
termed a fo^e^. When a white smoke is seen 
to rise from the courses of rivers and wet land, 
it is called a misi; but mist and fog are often 
indiscriminately applied to the same appearance 
— namely, to a vapoury haze lying upon the 
ground. Clouds are the masses of haze or fog 
which are seen floating in the higher regions, 
and which do not descend to the ground. 

The steam of a kettle when it becomes visible, 
the white cloud of a steam-chimney, our breath in 
a moist or cold day, are all precipitated moisture 
or mist. Sometimes this mist is rapidly reab- 
sorbed as it spreads out, shewing that there is a 
certain dryness or vacancy in the air sufficient to 
take it in among the invisible steam, when it is 
distributed over a somewhat larger surface. 

If the air is exposed to a cooling, so as to bring 
it beneath the temperature of the dew-point, vapour 
must be thrown out everywhere, and a fog or mist 
will be formed. In this manner are formed the 
dense fogs of the polar seas, the fogs found 
along the courses of rivers, upon the sides 
of mountains, and over shoals and headlands. 
The celebrated fogs of London originate in the 
same way ; but their black and thick appearance 
is owing to the quantity of smoke which is sus- 
pended in them. 

The formation of clouds, as well as their 
frequent disappearance, can, in most cases, be 
readily explained by the general principles regard- 
ing the atmosphere and its vapour already laid 
down. Thus, we often see a clear morning gradu- 
ally become overcast with clouds. This arises 
from the sun's rays heating the earth, and causing 
currents of warm, moist air to ascend into regions 
where it is cooled by expansion below the dew- 
point, and part of its vapour is condensed into 
clouds. As the day declines, the process is 
reversed ; the cloudy particles descend and are 
dissolved, and a cloudless evening ensues. 

It is not uncommon to see the top of a hill 
wrapped in a stationary mist or cloud, even while 

• Besides the above, there are various instruments called 
hygrometers, depending on the principle of the shrinking and 
expanding of bodies in relation to the degree of humidity with 
which they are affected. Fibrous vegetable substances, such as 
ropes, contract by imbibing moisture ; while, on the contrary, 
hairs and catgut (strings of violins) contract by drought. Hair 
bas been found to be the most delicate in hygrometrical motions. 
Saussure accomplished the construction of a hygrometer from 
a single long hair, previously cleaned in a soda lye. Various 
philosophical toys, as ornaments for mantel-pieces, have also 
Seen constructed to indicate the dryness and moistness of the 
atmosphere, all on the similar principle of contraction and 
expansion of a hair, piece of catgut, or part of the beard of the 
wild oat. 
36 



a pretty rapid breeze is blowing over it. The 
explanation is simple. The current of air, in 
crossing the hill, rises into a region where the 
temperature is below its dew-point, and part of its 
vapour is there condensed into mist ; but, as it 
descends the other side, it becomes warmer, and 
can again dissolve the watery particles. The sub- 
stance of the cloud is thus really in motion over 
the summit ; but it is constantly being shorn off 
on the lee-side, and as constantly receiving addi- 
tions on the other side, so that it appears motion- 
less as a whole. 

A question often asked regarding clouds is thus 
answered by Mr Buchan in his valuable Handy 
Book of Meteorology : 'A very natural inquiry is : 
How are clouds suspended in the air.? The 
example of a cloud appearing to rest on the top 
of a hill though a strong wind be blowing at the 
time, suggests an explanation. The cloud itself 
may appear stationary or suspended, but the par- 
ticles of which it is composed are undergoing con- 
stant renewal or change. The particles are upheld 
by the force of the ascending current in which they 
are formed ; but when that current ceases to rise, or 
when they become separated from it, they begin to 
fall through the air by their own weight, till they 
melt away and are dissolved in the higher tempera- 
ture into which they fall. Hence, as Espy has reas- 
oned, every cloud is either a forming cloud or a 
dissolving cloud. While it is connected with an 
ascending current, it increases in size, is dense at 
the top, and well defined in its outlines ; but when 
the ascending current ceases, the cloud diminishes 
in size and density.' 

The classification of clouds proposed by Luke 
Howard in 1803, is still universally followed. The 
three principal forms are the cirrus^ or feather- 
cloud, the cumulus, or heaped-cloud, and the 
stratus, or stretched-cloud. The cirrus is com- 




Cirrus. 
posed of thin threads or filaments, aggregated 
into woolly or feathery forms, and sometimes 
making a delicate, slender net-work. It is the first 
indication of serene and settled weather. The 
duration of the cirrus is uncertain — from a few 
minutes to several hours. It lasts longer, if it 
appears alone, and at a great height. From its 
usually curling anpearance, the cirrus is called in 




Cumulus. 
England the maris-tail cloud. The aimubis is 
the kind of cloud resembling mountains piled upon 
mountains, and generally ends above in rounded 



METEOROLOGY. 



masses, while it is horizontal below. The appear- 
ance, increase, and evanishing of cumulus, in fine 
weather, are often periodical, and correspondent to 
the degree of heat. Generally, it forms a few hours 
after sunrise, attains its highest degree in the 
hottest hours of the afternoon, and decreases and 
vanishes at sunset. If the upper region, with its 
drying power, predominates, the upper parts of the 
cumulus become cirrus ; but if the lower region 
predominates, the basis of the cumulus sinks, and 
the cloud becomes stratus, which appears as a 




.stratus. 

long horizontal band of moderate density, with its 
lower surface resting upon the earth or the water. 
Combinations of the above forms have been dis- 
criminated under the names of cirro-cumulus, 
cirro-stratus, and cumulo-stratus. The black rain- 
cloud, which seems a general mixture and con- 
fusion of all the clouds in the heavens, has been 
called the cumulo-cirro-stratus or nimbus. 

The cirrus clouds are the most elevated ; and 
must be often made up of snow-particles, for even 
under the equator, water would be frozen at such 
a height. In general, we may say of the light 
fleecy masses that we see on a summer-day, that 
they are made up of snow-powder or frozen par- 
ticles. The cirro-cumulus is formed from the 
cirrus by the fibres breaking and collapsing into 
small roundish masses. It is this which is known 
as a mackerel sky, and is attendant on dry and 
■warm weather. The cirro-stratus clouds consist 
of horizontal masses, dense in the middle and 
thinned towards the edges, so that a group of 
them resemble a shoal of fishes. Their prevalence 
indicates a coming storm. 

The cumulus clouds are evidently the precipita- 
tion of the ascending vapour in the cold upper 
regions ; for they generally increase with the heat 
of the day, which disperses all superficial mists. 
The stratus, on the other hand, has more the 
character of a night-cloud : it is a result of the 
cooling of the air in the evening, and comes out 
in the lower regions of the atmosphere. All mists 
and fogs are of this species of cloud ; which, in its 
lightest state, does not wet leaves or any objects 
•with which it comes in contact. Sometimes it 
remains quiet, and accumulates in layers, till the 
atmosphere is incapable of sustaining its weight, 
when it assumes the condition of the heavy and 
•dark nimbus, and falls in a shower of rain. 

The extreme height to which clouds may reach 
lias never been accurately determined ; but from 
•observations made in balloon ascents, it is probable 
that the cirrus cloud is often ten miles above the 
•earth. 

The average amount of the sky covered by 
clouds, is an important element in the climate of 
a country. It is usually measured by the scale of 
o to ID ; 5 indicating that the sky is half-covered, 
10 that it is wholly obscured. In Shetland, three- 
iburths of the sky is the average space covered 
with cloud ; the mean for the whole of Scotland 



is less than two-thirds, being 67 in the west, and 
6 in the east and interior. 

Dew. — When moisture is precipitated at night 
in the form of wetness, and drops on the surface 
of the ground and on the leaves of plants, it 
receives the name of dew. This precipitation 
arises when the surface of any body is cooled 
below the dew-point temperature of the air at 
the time. Thus, if the dew-point were 45°, and 
if by any means a glass tumbler were cooled 
down to 40°, the film of air lying next to it would 
also be cooled down to 40°, and would therefore 
have to give out all the vapour which it could not 
hold at that temperature ; but the precipitated 
surplus in this case would not appear as mist in 
the air, but would adhere to the surface of the 
glass. When cold glasses are brought into a 
warm room, they sometimes become dewed all 
over in this way. The bringing out of visible dew 
is, as we have seen, the means of determining the 
dew-point temperature in Daniell's hygrometer. 

Night-dews are most copious when the sky is 
clear. The reason of this is, that the earth cools 
faster under a clear sky than when hung over with 
dense clouds, which prevent the radiation of the 
heat ; just as bed-curtains make a bed warmer. 
Wind also prevents the deposition of dew ; because 
the air in contact with the earth is constantly 
changed, so that the temperature does not fall 
sufficiently low. The surfaces which naturally 
radiate off their heat with most rapidity are the 
first to sink below the dew-point temperature and 
to become dewed. Thus, rough surfaces are wetted 
sooner than smooth, plants sooner than glass, and 
glass sooner than metals. Metals being good 
conductors of heat, as fast as their surface cools, 
heat flows to it from the interior, and consequently 
the temperature of the surface cannot sink till the 
whole mass throughout has parted with its heat 
Woolly and fibrous substances cool very fast at the 
surface, and are therefore rapidly bedewed. No 
dew can fall on a surface till its temperature has 
fallen below the dew-point ; hence, in the case of 
a very dry atmosphere, there may be no dew formed 
at the coldest time of the night. In arid deserts, 
and in the countries where dry winds prevail, dew 
is not often seen. 

When the surface dewed is below the freezing 
temperature, the vapour is not only precipitated, 
but is also frozen ; hence the origin of hoar-frost, 
or frozen night-dew. The occurrence of hoar-frost 
is a proof that the temperature of the ground has 
fallen below 32°, as well as below the dew-point 
temperature. As in the case of dew, everything 
that prevents the radiation of heat arrests the 
formation of hoar-frost. During the chilly nights 
of spring, plants that are sheltered by trees are 
less liable to be frozen than those which are fully 
exposed ; and a slight covering of straw, or even 
of paper or netting, will often afford an effectual 
protection. Vineyards, it is said, have frequently 
been saved from the effects of frost by enveloping 
them during the night in a cloud of smoke. 

Rain is the aggregation of the cloudy particles 
into masses or drops. The causes of the formation 
of clouds have been already explained. Ever>' 
cloud does not end in rain ; it is only when the 
whole mass of air between the cloud and the earth 
is saturated, that the watery particles fall down. 

Snow.—^)xtn the temp)erature of the stratum of 
air from which the rain falls is under 32", the 

37 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



vapour or clouds must necessarily be frozen, and the 
descending particles will be snow instead of rain. 
Snow-flakes are the aggregation or union of frozen 
particles, just as rain-drops are the union of watery 
particles. They aggregate, according to the law 
of the cr>'stallisation of water, into regular and 
symmetrical forms, of which the general character 
is a six-sided figure ; as, for example, six needles 
branching from a centre, or six arms from a six- 
sided nucleus, each needle being three or six sided. 
Though single crystals always unite at angles 
of 30°, 60°, or 120°, they nevertheless form, by their 
different modes of union, about 1000 distinct 




varieties of snow-flake, some of which are figured 
in the preceding engravings. Any agitation of the 
air, or an increase of moisture or temperature, 
destroys, of course, their delicate and beautiful 
structure. 

Hard pieces of ice falling in showers are called 
hail. The mode of their formation is not clearly 
understood. The sudden ascent of moist air into 
the upper regions, where it encounters a cold 
current, is probably the common cause of hail. 
Hailstones vary in shape, and when cut across are 
found to be composed of alternate layers of clear 
and opaque ice, enveloping a white nucleus. Many 
of them seem to be agglomerations of several hail- 
stones. They vary in size from the smallest shot 
to several inches in diameter. 

Besides tiitrogen, oxygen, and watery vapour, 
the atmosphere contains minute quantities of 
numerous other substances — carbonic acid, am- 
monia, ozone, exhalations of all kinds, dust, seeds 
or germs of plants and animalcules, &c. But, 
however important some of them may be in the 
economy of nature, the consideration of them 
does not properly belong to meteorology. 

SURFACE OF THE EARTH IN RELATION TO 
THE ATMOSPHERE. 

Mean Temperature — Trade-winds — Sea and Land Breezes — 
Hygrometric Changes— Fall of Rain— Fluctuations of the 
Barometer and Thermometer. 

The changed and fluctuations of the atmosphere 
have all a relation to the peculiarities of the earth's 

38 



surface, and especially to the unequal heating of 
its different parts, owing to the varied action of 
the sun, the distribution of sea and land, and the 
different elevations of the land. 

By the mean temperature of a place is under- 
stood the average temperature for a whole year, 
or for a number of years. If observations were 
made of the temperature for every hour in the 
course of a day, the average of all these would be 
the mean temperature of the day ; also the mean 
of the greatest and least temperatures would be 
pretty nearly the mean of the day. If the mean 
temperatures of 365 days are found in this way,, 
and an average taken of the whole, this gives the 
average or mean temperature of the year. And if 
a great many years have been observed in the 
same manner, the average of the whole would be 
reckoned the general mean temperature of the 
place where the observations have been made. 

The action of the sun is the chief source of the 
warmth possessed by the atmosphere and the 
ground, though not the only source (see Geology 
and Physical Geography). 

The reason why the sun heats the equator and 
the regions adjoining more strongly than it heats 
the temperate and polar regions, is, that at the 
equator it rises higher in the heavens, and shines 
more directly downwards. The farther away a 
place is from the equator, the less is the average 
noonday height of the sun, and therefore the 
smaller the influence it exerts. 

The mean temperature of the equator is about 
80°. If the whole earth were a perfectly smooth 
globe of one uniform kind of surface — that is, if it 
were all sea, or all one kind of level land — the 
temperature would decrease steadily from the 
equatorial amount, according to the latitude ; but 
the variations of the surface cause many important 
deviations. 

The whole force of the sun's rays does not act 
directly on the solid surface of the earth ; the 
atmosphere, especially when charged with vapour, 
arrests a certain portion of the heat, and is itself 
rendered warm by the portion arrested. This is 
one source of the warmth of the air. When clouds 
are spread out in the atmosphere, the resistance 
to the rays is still further increased, and a greater 
portion taken up by the air itself. The other 
sources of atmospheric heat are, contact with the 
surface of the earth, and the radiation of heat from J 
the ground upwards. 

The air exercises a very important influence in 
keeping up the mean temperature of the earth, by 
resisting the passage of heat outwards, on the 
same principle that our bodies are kept warm by 
clothing. The thinner the covering of air, the 
colder would the earth be ; as we see in ascending^ 
to the tops of mountains, at which the temperature 
is always much lower than at the sea-level — the 
cold increasing with the height. These high places 
receive a more intense solar radiation through the 
thin covering of air that lies upon them ; but such 
is the ease with which the heat can radiate off 
through a thin atmosphere, that they are always- 
kept comparatively cold. If we had no atmosphere 
at all, the rays of the sun would be very intense 
where they actually struck, but so rapid would be 
the loss of heat by radiation, that the whole earth 
would be permanently kept far below freezing ; no 
liquid material of any known kind could exist on 
its surface. 



METEOROLOGY. 



Trade-winds. — The first great effect on the 
atmosphere of the unequal temperature of the dif- 
ferent parts of the earth, and especially of the 
steady decrease of heat from the equator to the 
poles, is to produce the two grand currents which 
we have already described : an upper-current from 
the equator to the poles, and an under-current 
from the poles to the equator. If the earth were 
at rest, these currents would blow exactly north 
and south, but the daily revolution of the globe 
has an effect in altering their directions. The 
equator, or thickest portion of the earth's body, 
considered as a ball revolving on an axis, moves 
with the greatest rapidity in the daily whirl ; any 
place upon it is carried round at the rate of 
upwards of looo miles an hour. But the belts on 
each side of the equator being smaller in circum- 
ference, any point on one of them is moved with 
proportionably less rapidity. Thus the belt or 
zone at 60° of latitude has only half the circum- 
ference of the equatorial zone ; so that a place 
upon it will move round only 500 miles an hour. 
Now the atmosphere revolves along with the 
earth, and every portion of it will have the same 
velocity as the place on which it lies. But if 
the equatorial air, with its high velocity, is carried 
away in the upper-current to a place with a lower 
velocity, the air will still persevere in its equatorial 
speed, and will consequently outrun the speed of 
the place upon which it has come, and be felt as 
a strong wind in the direction of the rotation. 

A similar explanation serves to shew that the 
under-currents from the poles to the equator will 
not be due north and south, but will have, in addi- 
tion, a direction towards the west. 

According to this simple theory, the prevailing 
winds ought everywhere on the earth's surface to 
be easterly: in the northern hemisphere, they 
should blow from the north-east ; in the southern 
hemisphere, from the south-east. And at sea 
within the tropics, and to some distance beyond 
them, this is in fact the case. The great polar 
currents are there known by the name of the trade- 
winds, because they are so constant that they can 
be calculated on by navigators. The trade-winds 
begin to be felt at about 30° of latitude on each 
side of the equator. Ships entering upon this belt 
begin to feel a steady easterly breeze, which con- 
tinues, although with some variation, to within 2° 
of the equator. The two currents from north and 
south meet about the equator, and completely 
neutralise each other ; and their meeting forms a 
belt varying from 150 to 550 miles in width, called 
the region of calms and variables. There is no 
steady wind in this region ; its atmosphere is 
generally calm, having at certain seasons light 
southerly winds, interrupted by fearful storms and 
tornadoes. 

Beyond the region of the trade-winds, the pre- 
vailing currents are in the opposite direction — 
in the northern hemisphere, for instance, from the 
south-west. To account for this, we must suppose 
that the two great currents change places, and 
that about the latitude of 30° the upper equatorial 
current descends to the surface of the earth. 

The region of the south-east trade-winds is much 
larger than that of the north-east, the belt between 
them lying generally not at the equator, but several 
degrees north of it. The entire belt of the trades 
shifts in some degree northwards in summer, and 
southwards in winter, following the courseof thesun. \ 



Direct proofs have been furnished that in the 
regions of the trade-winds there are upper return- 
currents flowing in. the contrary direction. The 
ashes of the volcano of St Vincent, on one occasion 
were carried from west to east, to the astonish- 
ment of the inhabitants of Barbadoes, who were 
experiencing at the time the easterly wind. 

Sea and Land Breezes.— The great polar and 
equatorial currents are modified by another class 
of currents, of a more local character, arising from 
the unequal susceptibility of the sea and the 
land to the sun's heat. If the sun shine with the 
same directness and force on two tracts of surface 
the one water, and the other solid ground, the 
ground will be most rapidly heated, and at the 
end of the day it will be found much warmer than 
the water. On the other hand, in the absence of 
the sun, the land cools fastest, and at the end of 
the night it will be found below the temperature 
of the adjoining water. This difference causes an 
inequality in the temperature of the columns of air 
lying upon the two surfaces. When the land is 
hottest, the air resting upon it will be hotter and 
lighter than the air over the sea ; hence the cold 
air from the sea will rush in upon the hot. Thus 
during the day, when the land is warmer than the 
sea, there will be a breeze from the sea to the 
land, and during the night, a breeze from the land 
to the sea. These sea and land breezes are felt 
regularly on all the sea-coasts when not overborne 
by other winds. 

Monsoons.— ^hext. a large tract of land joins a 
great expanse of sea, as on the coasts of America 
and the south of Asia, the sea and land breezes 
become very considerable. The easterly trade- 
winds are often reversed by them. But the most 
powerful effect of the sea and land winds is annual, 
or dependent on the seasons. The most remark- 
able example of this is furnished by what are 
called the monsoons — from the Arabic word mau- 
sittt, a set time or season — experienced along the 
coasts of Africa, India, and China. When the sun 
is far north in midsummer, and shines with direct 
rays on the Asiatic peninsulas, the land in them is 
rendered very much hotter, both day and night, 
than the ocean, and a strong sea-wind sets in 
towards these coasts from the south-west — that is, 
in a direction opposite to the great current that 
causes the trade-winds. Hence an immense wide- 
spreading conflict arises, which begins about the 
month of April, or two months before the sun 
has reached his extreme north declination. The 
beginning of the conflict in April causes furious 
rain, wind, and thunder-storms ; but in the course 
of two or three weeks the sea-breeze completely 
overcomes and suspends the trade-wind, and con- 
tinues steadily to prevail from April to October ; 
this is called the south-west monsoon; and it can 
be as much calculated on for navigation as the 
trade-winds in their most uninterrupted regions. 
The influence which sustains this wind becomes 
gradually weaker as the sun moves southward, 
and in October it becomes too weak to overcome 
the trade-wind, and the two meeting with equal 
force, cause a second violent tumult of rain and 
storms, till in a short time the trade-wind prevails ; 
which then continues during the winter half-year, 
and forms what is called the north-east monsoon. 

In the Atlantic, a similar action is perceived. 
In the summer-time, the land of North Africa is 
made so much hotter than the adjoining sea, that 

39 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



a brisk south-west or south-south-west wind blows 
between the equator and the southern limit of the 
northern trade, which is then at about io° or 12° 
north latitude. In America, also, similar breezes 
are experienced. 

Rainfall* — The chief sources of evaporation 
are the seas, lakes, and rivers. Although there 
is three times as much sea as land, this is not 
more than enough to keep up a sufficient mois- 
ture for the habitable countries ; for although 
some regions have rather more than is desirable, 
many large tracts of country remain desert and 
uninhabitable solely from the dryness of their air 
and the scarcity of rain. 

The evaporation is necessarily greatest in the 
equatorial regions, where the temperature is 
greatest, and decreases steadily towards the 
poles. And although a great deal of the tropical 
evaporation is transported by air-currents into 
higher latitudes, the precipitation of vapour, or 
the rain, is also most abundant in the warmest 
climates, and in the neighbourhood of the trop- 
ical seas. 

Rain is the most capricious of all the meteor- 
ological phenomena, both as regards its frequency 
and the amount which falls in a given time. It 
rarely or never falls in certain places, which are, 
on this account, designated the rainless regions 
of the globe — the coast of Peru, in South America ; 
the great valleys of the rivers Columbia and Colo- 
rado, in North America ; Sahara, in Africa ; and 
the Desert of Gobi, in Asia, are examples ; whilst, 
on the other hand, in such places as Patagonia, 
it rains almost every day. Again, the quantities 
which have been recorded at some places to have 
fallen at one time, are truly enormous. In Great 
15ritain generally, if an inch fall in a day, it is 
considered a very heavy rain. In many parts 
of the Highlands of Scotland, three inches not 
unfrequently fall in one day. On the 5th of 
December 1863, there fell at Portree, in Skye, 
12^ inches in 13 hours. At Seathwaite, in 
Borrowdale, 662 inches fell on November 27, 
1845. But it is in continental, and especially 
tropical countries where the heaviest single 
showers have been recorded. The following are 
a few of the most remarkable : At Joyeuse, in 
France, 3i'i7 inches fell in 22 hours ; at Geneva, 
30 inches in 24 hours ; at Gibraltar, 33 inches in 
26 hours ; on the hills above Bombay, 24 inches 
in one night ; and on the Khasia Hills, 30 inches 
on each of five successive days. 

The heaviest annual rainfall on the globe is 600 
inches on the Khasia Hills, about 500 inches of 
which falls in seven months during the south- 
west monsoons. This astonishing amount is due 
to the abruptness of the mountains which face the 
Bay of Bengal, from which they are separated by 
200 miles of low swamps and marshes. 

The following are some of the annual rainfalls 
in the tropics : Singapore, 97 inches ; St Benoit 
(Isle of Bourbon), 163 inches ; Sierra Leone, 87 
inches; Caracas, 155 inches; Pernambuco, 106 

* The quantity of rain which falls at any station during a given 
time is ascertained by means of the rain-^auge — an instrument 
constructed in various ways. One of the simplest forms consists 
of a cylindrical copper vessel furnished with a float ; the rain 
falling into the vessel raises the float, the stem of which is so 
graduated that an increase in depth, to the extent of one-hundredth 
of an inch, can be ascertained. It is observed that rain-gauges 
collect different quantities at different heights above the ground, 
the amount being always greater at the lower level. This remark- 
alile fact has never been quite accounted for. 
40 



inches ; Rio Janeiro, 59 inches ; Georgetown, 100 
inches ; Bahamas, 52 inches ; and Vera Cruz, 183 
inches. 

In general, when a mountain-chain crosses the 
course of an ocean wind, the weather-side is wet 
and the lee-side is dry. The trade-winds of the 
Atlantic sweeping over the continent of South 
America become cooled as they ascend towards 
the Andes, and, depositing their vapour, feed the 
mighty streams of the Amazon and Orinoco. 
On the west side of the wall of the Andes, in 
Peru, rain is almost unknown. 

Distribution of Atmospheric Pressure. — The 
varying pressure of the atmosphere, from place 
to place and from time to time, is the chief 
cause of all fluctuations of wind and weather. 
A knowledge, therefore, of the distribution of this 
pressure over the globe, and the laws of its 
changes, as indicated by the barometer, is the 
basis of meteorology. Variations of the barom- 
eter are of two kinds — periodical and irregular. 
Of the regularly recurring variations, the daily 
variation is of small amount, and of little direct 
importance. The phenomenon has its cause in 
the daily march of the sun round the globe. 
The annual variation follows the march of the 
sun from one side of the equator to the other. 
The greater power of the sun in the northern 
hemisphere in summer rarefies the air, and 
causes a transference of a part of it into the 
colder southern regions, thus diminishing the 
pressure. The presence of a greater proportion 
of vapour acts in the same direction, owing to 
vapour having less specific gravity than dry air. 
As a rule, then, the atmospheric pressure is least 
in the summer, and greatest in the winter, in each 
hemisphere. But this annual fluctuation is subject 
to much greater local differences and anomalies 
than is the daily. Thus, in Siberia, the pressure 
is tV^s of an inch less in July than in January. 
The great heat of Siberia in summer causes the 
air to expand and flow away in all directions. 
In winter, on the other hand, the great cold and 
small rainfall of that region cause high pressures 
to prevail. In Iceland and Orkney, again, the 
reverse of all this holds : the pressure is least 
in winter, and greatest in summer. The summer 
temperature of the North Atlantic, in which these 
islands are situated, is cool as compared with the 
heated continents that enclose it, hence there is 
an overflow from these regions into the basin of 
the North Atlantic, and therefore increased pres- 
sure ; while in winter, the temperature there is com- 
paratively high, causing an overflow of air towards 
adjoining countries, and a diminished pressure. 

The distribution of atmospheric pressure is best 
exhibited by means of isobarometric charts; that 
is, charts on which lines are drawn through all 
places where the height of the barometer is the 
same. Such a chart may represent the mean 
pressure for the year, or the mean for a portion 
of the year, such as a particular month ; or the 
readings of the barometer at a specified moment, 
such as the beginning or middle of a storm. 
Owing to the immense labour of collecting and 
arranging the hundreds of thousands of observa- 
tions necessary for such a purpose, it is only 
recently that the attempt has been made. Mr Alex- 
ander Buchan, Secretary of the Scottish Meteorol- 
ogical Society, has the merit of first undertaking 



METEOROLOGY. 



the task ; and a chart for the year, and one for 
each of the two months of July and January, 
pubhshed in his Handy Book in 1868, are the first- 
fruits of his labours. Ten more charts are to 
follow, so as to exhibit the progress of the annual 
variation, with its anomalies, throughout the year. 
It is easy to conceive that such a system of lines 
must throw great light on all inquiries regarding 
prevaiHng winds, the varying temperature, and 
the rainfall over the world. 

The insight into the causes of atmospheric 
changes afforded by these charts, may be judged of 
from what Mr Buchan says in describing that for 
January : ' Over the North Atlantic occurs an exten- 
sive diminution of pressure, which deepens north- 
wards till the greatest depression, 29-5, is reached 
in Iceland, or perhaps in a slightly lower depres- 
sion nearly midway between that island and 
Spitzbergen. The widening of the isobarometric 
curves of 29*6 and 297 inches to the westward 
over Greenland, and to the eastward over the 
north of Norway and Russia, is an interesting 
feature of this area of low pressure. The low 
pressure of this region is due to the saturated 
state of its atmosphere and to the copious rainfall 
resulting from it. The flow of the Gulf-stream 
north-eastwards through the Atlantic to at least 
beyond Spitzbergen, and the larger amount of 
vapour poured into the atmosphere from its 
warmer waters, tends still further to lower the 
pressure. It is this low pressure over the North 
Atlantic, together with the high pressure to the 
eastward over Asia, which forms the key to the 
explanation of the winter climate of Europe.' 

Distribution of Terrestrial Temperature. — The 
temperature of the earth differs not only in differ- 
ent regions of its surface, but at different eleva- 
tions above or below the surface. In ascending 
a mountain or into the air in a balloon, the ther- 
mometer, as a rule, falls. The rate generally 
allowed is 1° of Fahr. for every 300 feet.* The 
increase of cold at high elevations arises from 
several causes. One cause is the rarefac- 
tion of the atmosphere, which takes place on 
ascending (see No. 15). Under ordinary cir- 
cumstances, when a gas is allowed to expand, its 
temperature falls. This used to be explained by 
saying, that a gas when rarefied has a greater 
capacity for heat, and therefore requires a greater 
absolute quantity to keep it at a certain tempera- 
ture. There is really, however, no change of 
specific heat, for it is possible, under certain 
conditions, to rarefy a gas without any loss of 
temperature. The real cause is that the gas in 
expanding performs workj it puts itself in motion 
to occupy the wider space, and no motion can be 
caused without expending some form of energy. 
The temperature of the gas depends upon some 
kind of oscillating motion among its molecules ; 
part of this molecular motion is converted into a 
motion of translation, and the energy or heat 
of the gas is diminished by the amount thus 
expended. Another cause is found in the fact, 
that the sun's rays have little effect on the atmos- 
phere, especially when dry, and only give out 
their full heat when they strike solid objects. It 
is thus the lower strata of the air that are in 

• According to the experiments made by Mr Glaisher in 
balloons, the diminution of temperature is 7-2' F. for the first 
thousand feet, but only 5-3* F. between the first and second 
thousand. From 14,000 to 15,000, it is reduced to 2-i*. 



contact with the warm earth that derive most beat 
from the sun's rays. In addition to all this, the 
radiation, or loss of heat, goes on more rapidly, 
there being no solid objects around to return it, 
and the rarer air opposing less obstacle to its 
escape. At considerable elevations, too, there is 
proportionally less vapour in the air ; and as it is 
the chief obstructor of radiation, objects in high 
regions are exposed naked, as it were, to the cold 
of the outer universe. At a certain height over 
every place, water will freeze, and if a mountain 
rise to this height, it will be covered with snow. 
The height over any place where water must be 
frozen at all seasons is called the snow-line^ the 
altitude of which is greatest at the equator, and 
diminishes as the latitude increases. At a certain 
high polar latitude, it reaches the mean sea-level ; 
that is to say, the ground at that level is eternally 
clad with snow.* 

The law, however, of loss of temperature by 
elevation is subject to important exceptions. In 
winter, the earth is losing more heat by radiation 
than it derives from the sun's rays ; therefore, 
in a dry, calm, clear night, the surface rapidly 
loses heat, and the stratum of air in contact with 
it is thus chilled below the general temperature of 
the atmosphere. The effect is most marked at 
short heights above the surface. The air in con- 
tact with the ground is frequently 15° or 20° below 
the air four feet above the ground ; above four feet 
the differences are comparatively small It is 
evident from all this, that in comparing thermom- 
eters, it is important that they be placed at the 
same height above the surface. 

The effect of this chilling of the lower stratum 
of the atmosphere is modified by the configuration 
of the surface. From off heights and slopes, the 
chilled air flows down into the low-lying grounds, 
and there accumulates. 

* This explains,' says Mr Buchan, 'why vapour 
becomes visible so frequently in low places, whilst 
adjoining eminences are clear ; and the same fact 
instinct has made known to cattle and sheep, 
which generally prefer to rest during night on 
knolls and other eminences. Along most of the 
water-courses of Great Britain, during the memor- 
able frost of Christmas 1 860, laurels, araucarias, and 
other trees growing below a certain height were 
destroyed, but above that height they escaped.' 

The variations of temperature below the surface 
belong rather to Geology and Physical Geo- 
graphy. 

We have now to consider how heat is distributed 
over the earth's surface horizontally. The causes 
of the varying quantities of heat enjoyed by dif- 
ferent places have already been described in a 
general way. The results of these causes, as 
modified by the varying relations of land and 
water, are made visible to the eye by means of 
charts having lines drawn through all places 
having the same temperature. These lines are 

* The sntrw-litu is found at various heights, according to 
latitude, proximity to the sea, and other causes, which affect the 
general climate of the region. In the Himalaya and Andes, it is 
found at an elevation of about 17,000 feet : in the Swiss Alps, at 
8500 feet ; and in the Scandinavian range, at 3500 feet. Gener- 
ally, in those countries which are near the equator, the snow-line 
is found about 16,000 feet, or three miles above the sea-level : 
about the 45th parallel in either hemisphere, it occurs at an eler»- 
tion of 9000 feet ; under 60* of latitude, at 5000 feet or thereby : 
under 70* latitude, at 1000 feet ; and under 80*, the snow-Uoe 
comes down to the mean sea-level : for countries which are 10* 
distant from the poles are covered with snow all the year round. 

41 



CHAMBERS'S INFORMATION FOR THE PEOPLE, 
called isothermals (Gr isos^ equal, thertne. heat), I when they mark mean annual temperature ; 




Fig. I. 

isotherals (Gr. theros, summer), when they mark I the hottest month, July ; and isocheimals, or iso- 
either the mean of the summer months or that of I chivienals (Gr. cheima or chima, winter), in regard 



no ISO 90 6£ SO 



60 9 J20 ^150 JBQ 




■.„,_L . ! \ "''• — -'-^ -^^^^3%p: 1 Ll:n^~. 



^^srr^- - — i J '^np^^ 



ISO " 120 90 Sli 30 




30 60 



Fig. 2. 



to winter. Fig. . i is such a chart, exhibiting the I while fig. 2 exhibits the hottest and coldest 
distribution of the mean annual temperature ; | months ; the dotted lines marking the mean 



METEOROLOGY. 



temperature of January, and the solid lines that 
for July. 

The part of the globe having the highest mean 
annual temperature forms an irregularly shaped 
belt, lying along the equator, and comprised 
between the north and the south isothermals of 
80°. On either side of this warm belt the tem- 
perature diminishes towards the poles ; and the 
lines shewing successively this diminution are, 
speaking in a very loose sense, arranged parallel 
to the equator, thus shewing the all-predominating 
influence of the sun as the source of terrestrial 
heat. The coldest portion of the earth's surface 
is a small oval-shaped patch near to but not 
surrounding the north pole, its mean temperature 
being —4°. Its narrowest diameter lies north and 
south, nearly touching the pole on the one side, 
and extending on the other as far south as 72°'3o 
N. lat. in 130° W. long. Part of it is seen in the 
diagram. 

While the decrease of temperature in advancing 
towards the poles corresponds in a general way to 
what may be called the solar climate, there are 
deviations brought about by disturbing causes too 
important to be overlooked. The chief of these 
disturbing causes are (i) the currents of the sea ; 
and (2) the prevailing winds. 

Of ocean-currents affecting temperature, the 
most marked and important is the Gulf-stream in 
the North Atlantic, which, by conveying warm 
water to the arctic regions, pushes the isothermals 
many degrees to the northward. There is a similar, 
though much feebler, current passing from the 
North Pacific to the Arctic Sea through Behring's 
Strait, and there, accordingly, the isothermals are 
pushed a little to the northward. An opposite 
effect is produced by two cold currents from the 
Antarctic Ocean, flowing, the one along the coast 
of Peru, the other along the west coast of Africa. 

Since winds bring with them the temperature 
of the regions they have crossed, the equatorial 
current is a warm wind, and the polar a cold wind ; 
also winds arriving from the ocean are not subject 
to such variation of temperature during the year 
as winds from a continent. As an atmosphere 
loaded with vapour obstructs both solar and 
nocturnal radiation, it follows that moist winds 
are accompanied with a warm temperature in 
winter, and a cool temperature in summer ; and 
dry winds with cold winters and hot summers. 
The direction of mountain-ranges is also an 
important element to be taken into account in 
estimating the influence of winds on temperature. 
These considerations explain the position of the 
isothermals in the north temperate zone, where the 

Jrevailing wind is the south-west or anti-trade. 
n January, the western parts of each conti- 
nent enjoy a comparatively high temperature, 
from their proximity to the ocean, whose high 
temperature the winds waft thither ; and they are 
further protected from extreme cold by their moist 
atmosphere and clouded skies. But in the interior 
of the continents it is otherwise ; for the winds 
getting colder as they advance, and being deprived 
of their moisture as they cross the mountains in 
the west, the soil is exposed to the full effects of 
radiation during the long winter nights, and as a 
consequence, the temperature rapidly falls. In the 
centre of Siberia, the January temperature falls 
to —40°, which is 9° colder than the coldest part 
of the American continent ; and this centre of 



greatest cold lies near the eastern part of the con- 
tment of Asia. On the other hand, in July, the 
mterior of continents is much warmer than their 
western parts. Hence the interior and eastern 
parts of Asia and America are characterised by 
extreme climates, and the western parts by equable 
climates. Thus, at Yakutsk, in Siberia, the July 
temperature is 62°-2, and the January -43='-8 the 
difference being io6°-o; whilst at Dublin these are 
respectively 6o^-8 and 38°-5, the difference being 
only 22°-3. This constitutes the most important 
distinction of climates, both as respects vegetable 
and animal Hfe. On man especially the effect is 
very great— the severity of the strain of extreme 
climates on his system being shewn by the rapidly 
increasing death-rate as the difference between 
the July and January temperatures increases. 

Winds and Storms. — Winds are classed as 
Constant, Periodical, and Variable. The Trade- 
winds and Return Trades constitute the first 
class ; Sea and Land breezes, and Monsoons form 
the periodical class, and both have been con- 
sidered under the general movements of the atmos- 
phere. 

Variable winds depend on purely local or tem- 
porary causes, such as the nature of the ground,, 
covered with vegetation or bare; the physical 
configuration of the surface, level or mountainous ; 
the vicinity of the sea or lakes ; and the passage 
of storms. The hot, suffocating wind peculiar to 
Africa and Western Asia is known by the name 
of the Simoom; on the coast of Guinea it is 
called the Harmattan. A similar wind in Sicily 
and Italy is called the Sirocco, and in Spain the 
Solano. The East Winds which prevail in the 
British Islands in spring are part of the great 
polar current which at that season descends over 
Europe through Russia. Their origin explains 
their dryness and unhealthiness. It is a prevalent 
notion that the east winds in this country are damp. 
It is quite true that many easterly winds are 
peculiarly damp ; all that prevail in the front part 
of storms are very damp and rainy, and soon 
shift round to some westerly point. But the 
genuine east wind, which is the dread of the 
nervous and of invalids, does not shift to the west,, 
and is specially and intolerably dry. Deaths from 
brain-diseases and consumption reach the maxi- 
mum in Great Britain during the prevalence of 
east winds. The Etesian Winds are northerly 
winds which prevail in summer over the Medi- 
terranean Sea. They are caused by the great heat 
of North Africa at this season, and consist in a 
general flow of the air of the cooler Mediterranean 
to the south, to take the place of the heated air 
which rises from the sandy deserts. The Mistral 
is a steady, violent north-west wind, felt particu- 
larly at Marseille and the south-east of France,, 
blowing down on the Gulf of Lyons. 

Lord Bacon remarked that the wind most fre- 
quently veers with the sun's motion, or passes 
round the compass in the direction of N., N.E.,^ 
E., S.E., S., S.W., W., and N.W., to N. This 
follows in consequence of the influence of the 
earth's rotation in changing the direction of the 
wind. Professor Dovd of Berlin has the merit of 
having first propounded the Law of the Rotation 
of the Winds, and proved that the whole system 
of atmospheric currents — the constant, the peri- 
odical, and the variable winds — obey the influence 
of the earth's rotation. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



The force of the wind is measured by Anemom- 
tters^ of which some measure the velocity, by 
the revolution of vanes, and 
others the pressure. Of the 
latter kind is Lind's Wind- 
gauge, represented in the 
figure. When the instrument is 
used, water is poured into the 
tubes until the level in both 
stands at the middle of the 
scale. When no disturbing 
force acts upon either column 
of liquid, the level of both is 
accurately the same ; but when 
the mouth of the tube AB is 
turned towards the wind, the 
column in AB is pressed down- 
wards, and that in CD rises 
proportionably, and the differ- 
ence of the heights of the two 
columns gives the column of 
water which the force of the 
wind sustains, and from this 
the pressure on a square foot is readily calculated. 




Dr I.ind's 
Anemometer. 



The following are a few velocities of wind, 
translated into popular language : 7 miles an hour 
is a gentle air ; 14 miles, a light breeze ; 21 miles, 
a good steady breeze ; 40 miles, a gale ; 60 miles, 
a heavy storm ; and 80 to 100 miles, a hurricane 
sweeping everything before it. We also add a few 
comparisons of velocity and pressure : 5 miles an 
hour is a pressure of 2 oz. on the square foot ; 10 
miles, i lb.; 20 miles, 2 lbs. ; 30 miles, 4^ lbs. ; 40 
miles, 8 lbs. ; 51 miles, 13 lbs.; 60 miles, 18 lbs. ; 
70 miles, 24 lbs. ; 80 miles, 32 lbs. ; and ico miles, 
50 lbs. During the storm in which the Tay 
Bridge was destroyed (Dec. 1879), the rate of 
velocity varied from 40 to 70 miles per hour, and 
the maximum velocity during the heaviest gusts 
was said to have reached 96 miles at Aberdeen. 
Wind is most frequently measured by estimation. 

The estimate of the wind's force by the scale o 
to 12, means that o represents a calm, and 12 a 
hurricane. If such estimations be divided by 2, 
and the quotient squared, the result will be the 
pressure in pounds, approximately. 

Storms are violent commotions of the atmos- 
phere, occurring in all climates, particularly in the 



t^fMT'^i r\. Vs. 





tropics, and differing from other atmospheric dis- 
turbances in the extent over which they spread 
themselves, their-destructive power, and the sudden 
changes which take place in the direction of the 
44 



wind. Numerous attempts have been made to 
reduce the phenomena of storms to general laws ; 
but it is only quite recently that observations have 
been sufficiently numerous and accurate to furnish 



METEOROLOGY. 



the necessary grounds. The foregoing chart of 
Europe shews, from actual observations made at 
upwards of loo localities scattered over that 
continent, the barometric pressure, and direction 
and force of the wind, at 8 A.M. of the 2d of 
November 1863, during part of the course of 
two storms which passed over Europe at that 
time. At the same hour of the previous day, the 
centre of the first storm (I.) was near Christian- 
sund, and that of the second was approaching the 
west coast of Ireland. The isobarometric lines, or 
lines shewing where, at the above hour, the height 
of the barometer was the same, are given for every 
two-tenths in the difference of the pressure. Hence, 
where these lines approach near each other, or 
crowd together, the difference of pressure, or the 
atmospheric disturbance, was the greatest ; and 
the least where they are most apart — a distinction 
of the utmost importance in determining where 
the storm may be expected to rage in greatest 
fury. The arrows shew the direction of the wind, 
being represented flying with it. The force of the 

wind is shewn (i) by plain arrows, ^, which 

represent light and moderate winds ; (2) by arrows 
feathered on one side only, w " '> , which represent 
high winds ; (3) by arrows feathered on both sides, 
<«f — >, which represent strong gales, storms, or 
hurricanes. 

Form and Extent of Storm Areas. — ^The cir- 
cular isobarometric lines on the chart represent 
very accurately the general shape storms assume. 
The area of almost every storm is either circular 
or slightly elliptical. The outline is occasionally 
veay irregular. The extent over which storms 
spread themselves is very variable, being seldom 
less than 600 miles in diameter, but often two or 
three times that amount, or even more. 

Direction in which Storms advance. — It may 
be premised that by the direction of a storm is 
meant, not the direction of the wind, but the 
path followed by the centre of disturbance. The 
direction in which this progressive motion takes 
place differs in different parts of the world — being 
determined by the prevailing winds. Thus, 
about half the storms of Middle and Northern 
Europe travel from the south-west toward the 
north-east, and 19 out of every 20, at least, travel 
toward some point in the quadrant from the 
north-east to the south-east. Observation shews 
that the longer axis of the storm is almost 
always coincident with the direction in which 
the storm appears to be moving at the time. 
The storms of the Mediterranean follow a differ- 
ent course. Many of them proceed from the 
north to the south, influenced probably by the 
heated air rising from the Sahara. By far the 
greater number of the storms of North America 
take their rise in the vast plain which lies imme- 
diately to the east of the Rocky Mountains, 
and thence advance in an eastern direction over 
the United States ; some of them, crossing the 
Atlantic, burst on the western shores of Europe. 
But the relation of the American to the European 
storms is not yet established. The storms of the 
West Indies generally take their rise from near the 
region of calms, and tracing out a parabolic course, 
proceed first towards the north-west, and then 
turn to the north-east about 30° N. lat., many of 
them traversing the east coasts of North America 
as far as Nova Scotia. South of the equator they 
follow an opposite course. The hurricanes of 



Hindustan usually pursue a parabolic path, first 
traversing the eastern coast towards Calcutta, and 
then turning to the north-west up the valley of 
the Ganges. The typhoons of the Chinese seas 
resemble, in the course they take, the hurricanes 
of the West Indies. Observations are wanting 
from other parts of the world to determine the 
course of storms. 

Everywhere, the course tracked out by storms 
is determined by the general system of winds 
which prevail, modified by the unequal distribution 
of land and water on the surface of the globe. 
Facts seem at present to point to this general 
conclusion, viz., Storms follow the course of tht 
atmospheric current in which the condensation of 
the vapour into the rain which accompanies them 
takes place. 

The Rate at which Storms travel^ varies from 
15 or 17 miles an hour in Europe, to 30 or 40 
miles in tropical countries. 

Relations of Temperature, Rain, and Cloud to 
Storms. — The temperature increases a few degrees 
at places toward which and over which the front 
part of the storm is advancing, and falls at those 
places over which the front part of the storm has 
already passed. In other words, the temperature 
rises as the barometer falls, and falls as the barom- 
eter rises. When the barometer has been falling 
for some time, clouds begin to overspread the sky, 
and rain to fall at intervals ; and as the central 
depression approaches, the rain becomes more 
general, heavy, and continuous. After the centre 
of the storm has passed, or when the barometer 
has begun to rise, the rain becomes less heavy, 
falling more in showers than continuously ; the 
clouds break up, and fine weather ushered in with 
cold breezes ultimately prevails. It should be here 
remarked, that if the temperature begins to rise 
soon and markedly after the storm has passed, a 
second storm may be expected shortly. The rain- 
fall is generally proportioned to the suddenness 
and extent of the barometric depression at the 
place where it falls. 

Direction and Force of the Wind in Storms. — 
If the winds in Storm II. on the 2d November 
be attentively examined, they will be observed 
whirling round the area of low barometer in a 
circular manner, and in a direction contrary to 
the motion of the hands of a watch, with — and 
be this particularly noted — a constant tendency to 
turn inwards towards the centre of lowest baro- 
meter. The wind in storms neither blows round 
the centre of lowest pressure in circles, nor does 
it blow directly towards that centre, but takes a 
direction nearly intermediate. In other words, 
the whole atmospheric system flows in upon the 
centre in a spiral course. This rotatory pecu- 
liarity is common to all storms in the northern 
hemisphere that have yet been examined. In the 
southern hemisphere, a rotatory motion is also 
observed round the centre of storms, but it takes 
place in a contrary direction, or in the direction 
of the motion of the hands of a watch. 

Professor Taylor has the merit of having first 
applied Dove's law of rotation to explain the 
direction of the rotation of storms round their 
centre. The cause may be seen by referring 
to Storm II. on the 2d November. On that 
morning, the pressure over England being much 
less than in surrounding countries, if the earth 
had been at rest, air-currents would have flowed 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



from all directions to England, to fill up the 
deficiency, in straight lines. The earth, however, 
is not at rest, but revolves from west to east ; and 
as the velocity of rotation diminishes as the lati- 
tude increases, it is evident that the current which 
set out, say from Lyon to the north, would, on 
account of its greater initial velocity when it 
arrived at Paris, blow no longer directly to the 
north, but to a point a little to the east of north ; 
in other words, it would no longer be a south, but 
a south-west wind. Again, since the current from 
the north of Scotland had a less velocity than 
those parts of the earth's surface on which it 
advanced, it lagged behind, and consequently, 
by the time it arrived at Silloth in the north 
of England, had changed from a north to a 
north-east wind. Similarly, the north-west current 
changed to a north, the south-west to a west, &c. 
Hence in a storm the whole system of winds 
rotates round the centre. It follows in the 
northern hemisphere that as storms advance, the 
general veering of the wind at places lying north 
of the path of their centre is from north-east by 
north to west ; and at places south of their centre, 
from north-east by east and south to north-west ; 
and conversely in the southern hemisphere. 

Next, as to the force of the wind : The rule is 
simple, and without exception — viz., the wind blows 
from a high to a low barometer, and with a force 
proportioned to the difference of the barometric 
pressures. Hence, where the isobarometric lines 
crowd together, the violence of the storm is most 
felt, and where they are far asunder, the winds are 
moderate and light. We have stated that the 
progressive motion of storms varies from 15 to 40 
miles per hour, which measures the time taken in 
passing from one place to another, but this gives 
no indication of the violence of the storm. This 
is determined by the rotatory velocity of the wind 
round the centre of the storm, which in Europe 
and America frequently amounts to 60 or 70 miles 
an hour continuously for some time. At Liverpool, 
on the 3d of December 1863, it blew in inter- 
mittent gusts with a speed of 93 miles an hour 
— a velocity frequently surpassed by storms within 
the tropics. 

Of the different theories of storms hitherto pro- 
posed, we need only refer to the rotatory and the 
centripetal theories. The rotatory, or, as it is com- 
monly called, the cyclonic theory, was first pro- 
posed by Piddington, and has since been elaborated 
by Redfield, Reid, Dov6, and others. By this theory 
storms are considered as revolving round an axis 
either upright or inclined to the horizon, while at 
the same time the body of the storm has a pro- 
gressive motion over the surface of the globe ; the 
barometric depression, as caused by the centrifugal 
force, driving the air from the centre to the circum- 
ference of the storm. A fatal objection to this 
theory is, that observation conclusively shews that 
the wind does nv^ rotate in a circle returning into 
itself, but constantly tends in a spiral towards the 
centre. Besides, the centrifugal force engendered 
by such a motion, even if it were a fact, would not 
be sufficient to depress the barometer at the centre 
to the hundredth part of the extent that actually 
takes place. 

' The spiral rotation,' says Mr Buchan, ' instead 
of the purely circular rotation, of the winds in 
storms, completely alters the whole complexion of 
the question of the theory of storms. For since it 

46 



follows from it that enormous quantities of air are 
constantly being poured all around into the area 
of the storm, and since, notwithstanding these 
accessions tending to increase the pressure, obser- 
vation shews that the pressure is not thereby 
increased, but on the contrary sometimes dimin- 
ished, we are forced to the conclusion, that from 
a large area within and about the centre of the 
storm a vast ascending current must arise into 
the upper regions of the atmosphere j and arriving 
there must flow away over into neighbouring 
regions. The physical cause of the ascending 
currents is to be found in the moist and warm, 
and therefore light, air which all observation 
shews to prevail in the front and in the central 
part of storms. And since most of the rain which 
accompanies storms falls in those parts of the 
storm, the barometer will be still further reduced 
by the removal of the elastic aqueous vapour 
which is condensed into rain-drops, and by the 
latent heat set free in the condensation of the 
vapour.' 

An important point is to be able to tell in what 
direction the centre of a storm is from the place 
at which we are, and the rule is easy : ' Standing 
back to the wind, the centre lies to the left hand of 
the direction in which the wind is blowing. This 
holds in all places north of the equator, and it 
furnishes the rule which must be observed by ships 
in steering out of the course of the storm. From 
this relation of the winds to the pressure is also 
deduced the rule for predicting the direction of the 
wind at particular sea-ports during storms. Thus, 
suppose at 9 a.m. it be required to know the 
direction in which the wind will blow in London 
at 9 P.M., a storm being observed advancing from 
Ireland towards the east. Information being had 
through the telegraph of the course the storm is 
taking, and an inference being drawn from that 
observed course that at 9 P.M. its centre will be 
near Liverpool, then at that hour the gale may be 
expected at London from S.S.W. 

Typhoons are violent storms that blow on the 
coasts of Tonquin, China, and Japan. They 
resemble the storms of Western Europe in their 
general characteristics, but the main features are 
more strongly marked. The central depression 
of the barometer is not unusually as much as 28-3 
inches, and, on rarer occasions, even 27 inches. 

Whirlwinds and Waterspouts. — Whirlwinds 
differ in many respects from storms or typhoons. 
They seldom continue longer than a minute at any 
place, and sometimes only a few seconds ; their 
breadth varies from a few yards to nearly a quarter 
of a mile ; during their short continuance, the 
changes of the wind are sudden and violent ; and 
the barometer is not observed to fall. They are 
caused by two air-currents coming in contact and 
causing an eddy. The direction of the eddy of 
the whirlwinds, especially when the diameter is 
very small, differs from the rotation of winds 
in a storm, in that it may take place either 
way — right to left, or left to right — according to 
the direction of the stronger of the two winds 
which give rise to the whirlwind. In the sandy 
deserts of the tropics, these eddies draw up with 
them large clouds of dust, and the whole is borne 
forward by the wind that may happen to be blow- 
ing at the time. 

Waterspouts are whirlwinds occurring on the 
sea or on lakes. When fCilly formed, they appear 



METEOROLOGY. 



as tall pillars of cloud stretching from the sea to 
the sky, whirling round their axes, and exhibiting 
the progressive movement of the whole mass pre- 
cisely as in the case of the dust whirlwind. The 
sea at the base of the whirling vortex is thrown 
into the most violent commotion, resembling the 
surface of water in rapid ebullition. It is a 
popular fallacy that the water of the sea is sucked 
up in a solid mass by waterspouts, it being only 
the spray from the broken waves which is carried 
up. 

What are sometimes called waterspouts on land 
are quite distinct from these phenomena. They 
are merely heavy falls of rain of a very local 
character, and may or may not be accompanied 
with whirling winds. 

Weather-forecasts. — From the direct bearing 
weather-changes have on human interests, they 
have from the earliest times been closely watched, 
so that the causes by which they are brought about 
being discovered, their approach might be pre- 
dicted with some degree of confidence. The crav- 
ing in the popular mind for this knowledge is 
strongly attested by the prognostics of the weather 
current in every language, which, amid much that 
is shrewd and of considerable practical value, 
embrace more that is vague, and not a little that 
is positively absurd. 

It may be laid down as a well established truth, 
that no prediction of the weather can be made, in 
the British Islatids at least, for more than three, 
cr perhaps only two days beforehand. Yet a belief 
in the prognostications of almanac-makers was 
once nearly universal, and is still prevalent. 

The Moon and the Weather. — The belief is 
almost universal, that the weather is influenced 
by the phases of the moon. A change of the 
weather, either from foul to fair, or from fair to 
foul, may be specially looked for, it is thought, 
at the times of new and full moon, or even at the 
quarters, though these last are not considered so 
influential. This belief is found to be altogether 
without foundation. 

The only predictions of the weather to be relied 
on are of the kind described in speaking of storms, 
where the telegraph comes into play. Almost all 
the weather-changes of Europe begin from the 
south-west, and pass over Great Britain to the 
north-east. Unsettled or bad weather is accom- 
panied with a low barometer ; elsewhere, the 
barometer is higher. Thus, then, suppose that, 
from weather-telegrams received, it is seen that 
■everywhere in Europe barometers are high, we 
may be sure that no storm need be dreaded for 
two days at least. But if, on the following morn- 
ing, barometers begin to fall a little in the west 
of Ireland, and an easterly wind begins to blow 
generally over Great Britain and Norway, and a 
south-east wind over France ; then, since the 
winds blow towards the lowest barometer, or 
rather a little towards the right of it, the presump- 
tion is that a storm of greater or less severity is 
coming up, the centre of which is likely to pass 
over England. This ought, therefore, to be closely 
watched by the telegraph, and the indications 
announced from time to time. 

It is our proximity to the Atlantic that makes 
it impossible to predict the weather beyond three 
days at the utmost. In Norway and the Baltic, 
and places towards the east of Europe, the weather 
may be predicted for a longer time, since each 



storm as it appears in the west may be followed 
in its course by the telegraph, and the places 
which it threatens be warned of the coming 
danger. In America also, where storms chiefly 
advance from west to east, gales and unsettled 
weather are predicted at the sea-board in the east 
some days before. 

But the collecting of this information by the 
telegraph is a work which, owing to the expense, 
governments only can accomplish ; and from its 
importance, it is an incumbent duty which they 
should discharge for the benefit of the seafaring 
population. 

From all that precedes, it will be clear enough 
that the mere height of the barometer, at a partic- 
ular place, taken by itself, affords no sure mdica- 
tion of what weather is coming ; so that the terms 
Rain, Fair, Set Fair, marked on the common 
weather-glass, are delusive. The quantity of 
vapour in the air, the temperature, and the direc- 
tion of the wind, are all to be taken into account 
And with regard to the barometer itself, it is not 
so much the actual height that is of consequence, 
as whether it is rising or falling, and whether the 
rise or fall has been of long duration. A slow 
rise continued for some days gives promise of 
settled weather ; a steady and long-continued fall 
indicates that a tract of unsettled and stormy 
weather may be expected. A sudden and great 
fall of the barometer is the sure forerunner of a 
violent storm. 



CLIMATE. 

The climate of a place depends on its distance 
from the equator, its height above the sea-level, 
its position in reference to oceans, seas, and con- 
tinents, the form of its surface, and the character 
of its soil. The points to be stated in reference 
to climate are, the mean temperature, the extreme 
winter and summer temperatures, the range of 
temperature daily, and from day to day, the 
humidity, the total fall of rain, the frequency of 
the falls, the relation of the amount fallen to the 
ordinary amount of vapour in the air, the pre- 
vailing winds, and the degree of variability of the 
weather. In general, the southern hemisphere of 
the globe is colder than the northern. 

The causes which determine most of these ele- 
ments of climate have been already described ; 
and the general results over the globe, as regards 
the most important element, temperature, are 
exhibited in the isothermal charts (page 42). 

Under the geography of Great Britain and 
other countries, the peculiarities of their several 
climates will be noticed. 



ELECTRICITY OF THE ATMOSPHERE. 

Thunder and Lightning— Aurora Borealls. 

The electric phenomena of the atmosphere 
possess great interest, but are as yet imperfectly 
understood (see Electricity). The discharges 
of the excitement are well known under the terms 
thunder and lightning, and they generally accom- 
pany storms and hurricanes, but rather as effects 
than causes. .- , 

The aurora borealis, one of the most beautatul 
of meteoric phenomena, is now believed to be 
connected with the magnetism of the earth. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



LUMINOUS METEORS. 
Rainbows— Halos— Parhelia — Coronx, &c. 

The various luminous appearances of the 
heavens, apart from the ordinary phenomena of 
sun, moon, and star light, are usually treated of 
under Meteorolog)'. 

The rainbow is owing to a complicated reflec- 
tion and decomposition of the rays of the sun in 
passing through drops of rain. It appears when 
the sun is unclouded, and rain is falling in the 
opposite quarter of the heavens. The mode of its 
formation is more particularly explained under 
Optics. A morning rainbow is an unfavourable 
prognostic of the weather ; a rainbow in the 
evening is favourable. 

Halos are coloured rings occasionally seen sur- 
rounding the sun or the moon. There are often 
several circles, some concentric, others intersecting 
or touching one another. They arise from the 
minute snow crystals of the cirrus cloud, and are 
due partly to refraction and partly to reflection. 
It can be shewn by the well-known principles of 
prismatic refraction, that the common halo of 22° 
radius is owing to refraction by the faces of the 
crystals that are inclined to one another at an 
angle of 60° ; while the wider circle of 46° radius 
is produced by faces at an angle of 90". At cer- 
tain points of the circles, other effects conspire to 
produce luminous knots called parhelia (mock- 
suns), or paraselenes (mock-moons). 

The true halos are to be distinguished from the 
corona that surround the sun or moon when a 
thin cloud passes over them. These depend on a 
different optical principle. The same appearances 
may be seen by looking at a candle through steam 
or through the dust of a room. The smaller the 
size of the particles, the greater is the diameter of 
the corona. A narrowing corona round the moon 
shews that the cloud particles are enlarging, and 
indicates coming rain. Coronas are less often 
seen round the sun, owing to the strength of his 
light. 

One marked distinction between coronas and 
halos is, that in halos the red prismatic colour is 
next the centre ; in coronas, the blue. 



IGNEOUS METEORS. 
Shooting-stars — Fire-balls — Aerolites. 

Shooting-stars are observed during serene nights. 
A luminous point like a star bursts into view, 
shoots a certain way through space, and then 
disappears. Sometimes it leaves a luminous train 
behind it; in other cases it gives forth sparks. 
These meteors have been noticed to occur in great 
numbers at once ; and the interest of such appear- 
ances has been very much increased by the fact 
of their being in some measure periodical. On 
several years they have been found to occur in the 
month of November. They also occur with some 
degree of frequency in August. Shooting-stars 
and fire-balls break out occasionally at every 
period of the year. 

It is now agreed that these bodies are nothing 
else than small planets, and, therefore, the con- 
sideration of them properly belongs to astronomy. 
There is every reason to believe that the planets, 
satellites, and comets are not the only bodies 

48 



which move round the sun, and lie within the solar 
system — they are merely the large conspicuous 
masses; while millions of others may exist, too 
small to be descried on ordinary occasions, and 
making themselves known by coming within the 
earth's atmosphere. The friction against the air^ 
caused by their immense velocity, develops enor- 
mous heat, which melts the surface of the body, 
and this outer liquid portion is thrown off in a 
long flaming stream forming the train, which, after 
losing its velocity, is precipitated to the earth as a 
fine dust or volcanic ash, while the meteor, thus 
rapidly diminishing, either becomes wholly dissi- 
pated into tail, or falls to the earth, or makes its 
way out of the atmosphere, and continues its 
course. The periodic meteors are small bodies : 
they have been calculated to range from 30 grains 
to 7 or 8 pounds, and none of them have been 
known to fall to the earth. These smaller bodies,, 
that are for the most part dissipated in the air» 
are the shooting-stars^ properly so called. The 
irregular or sporadic meteors frequently come to 
the earth in large masses, and often burst in fall- 
ing, owing to the outside being suddenly and 
intensely heated, while the interior remains cold. 
These aerolites (Gr. a'er, air, and lithos, a stone)- 
are found to consist of iron and stony matter 
in various proportions, the iron in some largely 
predominating. To account for the periodicity of 
the November meteors, it is imagined that a great 
number of them may move in a continuous ring or 
common orbit round the sun, so situated that the 
earth, in its annual course, brushes, as it were, 
with the outskirts of its atmosphere this ring of 
planetary fragments once a year. If the bodies 
were all round the ring, there ought to be a shower 
of them every November; but the great displays 
occur only once in about 33 years ; and there- 
fore it is inferred that the great mass of them are- 
grouped at one part, and that the time of revolu- 
tion of the ring being 33 years, that length of time 
must elapse between each concurrence of the earth 
and the dense part of the group. 

One of the most familiar of luminous meteors 
is the igfiis-fatuus, or ' Will-o'-the-wisp,' which 
appears at night on marshy grounds, places of 
sepulture, or wherever putrefaction and decompo- 
sition are going on. The appearance is that of a 
small flickering light, straggling in an irregular 
manner at the height of one or two feet from the 
ground, and sometimes standing for a few moments 
over a particular spot. When approached or pur~ 
sued, the lights are agitated by the motion of the 
air, and seem to elude investigation. The cause 
of this species of meteor has never been satisfac- 
torily explained. 

Until recently, meteorological observations had 
been mostly casual and without any uniform plan ;. 
hence the vagueness and uncertainty that hang 
over so much of the subject. But since 1840, the 
earth has been covered with a net-work of mete- 
orological observatories, maintained by the seve- 
ral European governments. Above all, the use of 
the telegraph in meteorology is proving a power- 
ful means both of advancing the science and of 
turning it to practical account. It is not un- 
reasonable to anticipate that, with the agents and 
apparatus now at work in this field, the next half- 
century may see light and order arising out o£ 
many things that now seem nothing but chaos. 



PHYSICAL GEOGRAPHY. 



GEOGRAPHY— from ^/, the earth, zndigrapho, 
I write — in its simple and literal significa- 
tion, is that science which describes the superficial 
appearance and conditions of our globe. It 
naturally divides itself into two great branches — 
I. Physical Geography, which treats of the earth 
as a superficies composed of land and water ; 
considers the position, extent, altitude, and general 
character of the former ; and the position, extent, 
depth, currents, and other motions of the latter : 
in short, all that relates to the distribution of land 
and water, variations of surface, temperature and 
climate, and distribution of plants and animals 
as dependent thereon, are the legitimate objects 
of this species of geography. 2. Political Geo- 
graphy, which treats merely of the division of 
the earth's surface by man into territories and 
states, describing their boundaries, the history 
of their occupation, their produce, commerce, 
population, laws, religion, and other topics which 
constitute the fundamental features of human 
polity. The latter of these branches will form the 
subject of several subsequent treatises ; to an 
exposition of the former — dwelling more on prin- 
ciples than on mere descriptive details — we intend 
to devote the present number. Before doing so, 
however, it will be necessary to advert briefly to 
the cosmical relations and constitution of our 
planet, as determined by astronomy, geology, 
chemistry', and meteorology. 



GENERAL CONSTITUTION OF THE GLOBE. 

Astronomy informs us that the earth we inhabit 
is one of a number o{ planets which revolve round 
the sun as a common centre, constituting what is 
usually denominated the Solar System. These 
planets are situated at different distances from 
the central orb, and differ also in their magnitudes, 
their densities, and in their periods of revolution. 
They are nearly spherical in form, are opaque, 
have no light of their own, but merely reflect that 
of the sun; and all move from west to east in 
nearly circular orbits. Several of them serve in 
turn as centres for other bodies of revolution, 
which are known by the name of satellites — as 
the moon, for example, which is the satellite or 
attendant of the earth. Besides the planets and 
their satellites, there is a third and numerous class 
of bodies belonging to the solar system — namely, 
comets, which revolve round the sun in regular 
periods, but in orbits so elliptical, that in parts of 
their course they approach nearer to the great 
orb than any of the planets, and in others recede 
so far into the regions of space, as to be entirely 
beyond the reach of our most powerful telescopes. 
The stars belong to other systems of revolution, 
and have, so far as has yet been determined, no 
perceptible effect upon the conditions of our globe, 
though undoubtedly bearing, like everything in 
nature, a universal harmonious relationship. 

The earth, as an individual planet, is situated 
at the mean distance of 91,350,000 miles from the 
sun ; has a mean diameter of 7912 miles ; per- 
forms a revolution round the sun in 365 days S 
4 



hours 48 minutes and 49 seconds, which consti- 
tutes the space of time called a year ; rotates on 
its own axis once in 24 hours— that is, in one day ; 
and in these movements is attended by the moon, 
which is distant 237,000 miles, is 2160 miles in 
diameter, and which completes her synodic revo- 
lution in 29 days 12 hours and 44 minutes, or in 
one lunar month. We have spoken here of the 
mean diameter of the earth, because, upon accurate 
measurement, it has been found to be not a perifect 
sphere, but an oblate spheroid, whose greater 
diameter is 7925, and whose lesser is only 7899 
miles. This gives a difference of 26 miles between 
the two diameters, or a flattening at each pole of 
about thirteen miles— a result that may be arti- 
ficially illustrated by twirling with rapidity a ball 
of any yielding material, such as putty, round a 
spit thrust through it as an axis, when a bulging 
at the outer circumference will take place, causing 
the ball to lose its original spherical form. This 
bulging takes place through what is called the 
law of centrifugal force ; and from what we know 
of this law, it is concluded that the earth was in a 
soft or yielding state at the time when it assumed 
its present form. Besides the bulk, revolutions, 
and configuration of our globe, science has also 
determined its density with considerable accuracy. 
By weighing the most prevalent rocks, it has been 
found that the solid crust composed of them is 
about two and a half times heavier than water ; 
but from experiments made on the attraction of 
mountains of known bulk, compared with the 
attraction and bulk of the globe, and by other 
means, it has been inferred that the density of 
the whole mass is five or six times that of water : 
in other words, the earth, as at present consti- 
tuted, is five or six times heavier than a globe of 
water of similar dimensions, and more than twice 
the weight of one composed of such rocky sub- 
stances as those with which we are acquainted. 
In addition to what may be called its own proper 
material, the earth is surrounded by a gaseous 
envelope or atmosphere. This atmosphere or air 
is peculiar to, and inseparable from, our globe — 
it rotates with the solid mass upon its axis, and 
does not, as may at first be supposed, occupy the 
space in which the rest of the heavenly bodies 
revolve. Like all aeriform and liquid masses 
whose particles press upon each other equally in 
every direction, the portions or strata next the 
earth are more pressed upon than those in higher 
regions ; and continuing this conception, a height 
must be arrived at where the air becomes so 
attenuated as to be inappreciable. That limit 
used to be assumed at 45 to 50 miles ; but there 
is evidence to shew that there is an atmosphere 
of some kind even at the height of 400 or 500 
miles. 

From its planetary relations, as a part of the 
solar system, the earth derives its figure and 
motions, its light and heat, and consequently the 
changes of season, and the alternation of day and 
night ; the phases of the moon, and the rising and 
faUing of the tides ; the vicissitudes of wind and 
weather, and all the varied results and phenomena 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



that flow therefrom. Thus, while its figure is 
preserved by the laws of centripetal and centrifugal 
force, its motions are determined and influenced 
by the attraction and gravitation of the sun and 
other planets. From its situation with respect to 
the sun, it necessarily follows that only one-half 
of its surface can be exposed at a time to the 
light and heat diff'used from that orb, thereby 
causing day in the one part, and night in the 
other. The seasons, again, are caused chiefly by 
the fact, that in performing its path round the 
sun, the earth preserves its axis in a slanting or 
oblique position, as has been more particularly 
explained in Astronomy and in Meteorology. 

The solar system, however, vast as it seems, is 
but a unit in space, which is peopled with other 
systems and orbs circling beyond the bounds of 
human conception. What we term^xed stars are 
but suns and centres of revolution ; and the solar 
system, as a whole, may revolve in space round 
some vast centre, just as its individual planets 
have their motions round the sun. From such a 
revolution may arise cycles of heat or cold, life 
or death, exuberance of certain living forms, and 
annihilation of others — cycles which meet with a 
faint analogy in the recurrences of our summers 
and winters. Even in the known relations of 
the earth to the sun, astronomers find causes of 
vicissitudes of temperature sufficient to account 
for those alternate periods of equatorial heat and 
glacial cold which geology shews our earth to 
have already passed through. 

The materials of 7vhich the earth is composed 
present a history not less curious than that of its 
planetary relations. Superficially speaking, the 
globe consists of land and water — the water occu- 
pying the extreme depressions of the land, and 
this land composed of solid or rocky materials. 
Our direct knowledge of these materials extends 
only to a small depth — a mere rind of the globe ; 
regarding the interior portions, we can only infer 
certain things. One of those inferences is that 
already noticed — namely, that the interior, as a 
whole, is more than twice as dense as the superficial 
matter. But whether this arises from the materials 
being different, or from their being more com- 
pressed, we have no means of knowing. It used to 
be held that the earth was a molten mass enclosed 
in a solid shell or cooled crust, through which the 
agitations of the liquid below produce the pheno- 
mena of volcanoes and earthquakes. From con- 
siderations, however, regarding the tides, and other 
astronomical data, it is inferred with certainty that 
this is not the case ; and it is most likely that at 
least half the distance from the surface to the centre 
is solid and more rigid than the rocks we know. 
The solid earth to which we have access consists of 
rocks, differing not only in their appearance and 
arrangement, but in their mineral and chemical 
characters ; some being compact and crystalline, 
as marble, others soft and dull, as chalk ; some 
lying in layers or strata, others occurring in huge 
irregular masses ; while, mineralogically and 
chemically speaking, we have such rocks as 
granite, quartz, slate, lime, coal, rock-salt, chalk, 
and clay. But the crust so composed, compact 
and solid as it may seem, is far from being per- 
manent and stable ; in other words, the dry land 
which now appears, with all its irregularities of 
hill and valley, plain and ravine, lake and river, 
is not the dry land which existed many thousands 
so 



of years ago. Strictly speaking, indeed, the aspect 
of the globe is ever changing. Here the sea 
encroaches on the land, there the ddbris borne 
down by rivers silts up bays and estuaries ; here 
earthquakes sink, and volcanoes elevate the sur- 
face ; lakes are dried up, and rivers change their 
course ; and, greater than all of these, vast regions 
gradually subside, and are covered by the ocean, 
while others as gradually emerge from the waters, 
and become dry land. All these changes, past 
and present, form the subject of geological con- 
sideration. 

Geology, in its aim to decipher the physical 
history of our globe, has determined that all the 
known rocks may be ranked under two great sec- 
tions — the stratified and the unstratified. The 
former appear in layers or beds, and have evidently 
been deposited in water, hence said to be aqueous 
or sedimentary J the latter appear in vast irregular 
masses, generally disrupting the stratified rocks, 




and have all the appearance of having been formed 
like the lavas of the present day ; hence they are 
called igneous or volcanic. Of the sedimentary 
rocks, sandstone, limestone, slate, and coal may 
be taken as illustrative examples ; of the igneous, 
granite, basalt, greenstone, and lava are the most 
familiar. As at present, so in all time past, the 
surface of the earth has been subjected to atmos- 
pheric, aqueous, and other influences, the effects 
of which are to wear down the exposed material ; 
and this, borne away by floods and rivers, is depos- 
ited in the ocean, where, consolidated by pressure, 
heat, and chemical agency, it forms new strata of 
rocks, which in time are brought to the surface by 
volcanic and other elevating forces. Thus, then, 
one set of agencies degrade, and another recon- 
struct and elevate ; and in proportion as either of 
these preponderate, so will any portion of the earth 
be low and level, or high and precipitous. Such, 
then, is the origin of the stratified and unstratified 
rocks — the one but the reconsolidated matter of 
pre-existing rocks, which have been worn and 
battered down by rains, frosts, waves, and rivers ; 
the other the cooled and hardened material sent 
forth from the interior of the earth by volcanic 
agency. But while rivers and floods bear down 
mud, sand, and the like, they also carry such 
vegetable and animal remains as lie in their 
course; and in this manner plants and animals 
are entombed in the newly formed layers or strata. 
As at present, so in former eras, such remaine 
have been enclosed in the stratified rocks, where, 
subjected to certain chemical agencies, they have 
become petrified, and are thus preserved as records 
of the former Flora and Fauna which peopled the 
globe. Geologists have, accordingly, found that 
the earth has not always been occupied by the 
same kinds of plants and animals that now exist ; 
but that different eras in its onward history have 
had very different Flora and Fauna, and that not 
one, perhaps, of the genera at one time in existence 
now survives. 

By long-continued and widely extended obser- 
vations in various parts of the globe, based on 



PHYSICAL GEOGRAPHY. 



numberless data of composition, structure, inclina- 
tion, and fossil contents, geologists have been able 
to form a definite list of the various rock-formations 
from the earliest to the most recent, arranged in 
the order of time. They have divided the whole 
•of the rocks composing the crust of the earth into 
sections called 'systems,' and have subdivided 
these again into * groups,' in a certain well-defined 
■order. So that when a rock is presented to their 
observation in any part of the globe, they can 
state, with more or less certainty, the system to 
which it belongs, and the period in the past his- 
tory of the earth at which it was deposited. See 
Geology. 

The constituents of all these rocks or strata, as 
well as those of plants and animals, are com- 
pounded of about sixty-three elementary sub- 
stances; of which, at the ordinary pressure and 
temperature of the atmosphere, five are gaseous, 
and the rest mostly solid, by far the greater 
number being metals. See Chemistry. 

Of the constitution of the ocean, or watery por- 
tion of the earth's superficies, chemical research 
affords us precise data. When pure, water is 
composed of i part of hydrogen and 8 oxygen by 
weight, or of 2 hydrogen and i oxygen by volume. 
In nature, however, water is generally found to con- 
tain many impurities — such as clay, sand, animal 
and vegetable matter, &c. — which, if left at rest, 
by their own weight soon fall to the bottom. Such 
substances are said to be mechanically suspended, 
and when deposited at the bottom, form sediment. 
Besides impurities of this description, water may 
contain matter which will not fall down, and which 
is said to be held in chemical solution. The saline 
matter in sea-water amounts to about 3^ per cent, 
of its weight, or nearly half an ounce to the pound. 
It consists chiefly of common salt, sulphate of 
soda, carbonate of lime, chloride of magnesia, and 
silica, although more than twenty other substances 
have been detected in minute quantity. The salt- 
ness of the sea, however, is not quite uniform. In 
general, it is greater in the trade-wind regions 
than in extra-tropical ; or wherever evaporation 
•exceeds precipitation. A rainless sea, like the Red 
Sea, is considerably salter than the ocean gener- 
ally ; the Baltic, again, which receives a great 
many rivers, and is besides shallow, contains only 
half as much salt as the Atlantic. It is often found 
that while a comparatively fresh current is flowing 
one way on the surface, a salter undercurrent is 
setting in the opposite direction. A knowledge of 
the constitution of the ocean is necessary to the 
explanation of numerous facts in geology and 
biology. 

The atmosphere, the next great constituent of 
the globe, plays an equally important part in the 
organic and inorganic economy. As it presses 
with a weight of about fifteen pounds upon every 
square inch at the ordinary sea-level, and dimin- 
ishes in density upwards in geometrical progres- 
sion, it is evident that animals and plants fitted to 
live at small elevations will die if removed to great 
heights — a circumstance corroborated by the fact, 
that travellers experience difficulty in respiration 
on very high mountains. Notwithstanding its 
transparency, the air intercepts and reflects the 
sun's rays, and propagates them by an infinity 
of repercussions ; and were it not for this pro- 
perty, objects would never be illuminated unless 
exposed to the direct light of the sun. The air — 



and more especially the watery vapour forming a 
part— is also the recipient and retainer of the heat 
radiated from the earth ; and were it not so con- 
stituted, the heat derived from the sun's rays would 
be returned to space, and an excessive cold con- 
tinually prevail. See METEOROLOGY. Chemically 
speaking, the atmosphere is a mixture of two gases, 
nitrogen and oxygen, in the proportion of 77 of the 
former to 23 of the latter, with about one part 
in 2000 of carbonic acid. In addition to these, 
which are its permanent constituents, there are 
always traces of ammonia and a certain amount 
of aqueous vapour, amounting from i to I "8 per 
cent. ; in certain localities, also minute quantities 
of other ingredients are to be occasionally detected. 
The atmosphere may therefore be regarded as the 
laboratory in which clouds, rain, snow, and other 
vapours are formed — the medium through which 
the light and heat of the sun are diffused and 
equalised — an element without which animal and 
vegetable life could not exist, for both incessantly 
inhale and exhale its elements ; and an agent 
indispensable to those innumerable physical oper- 
ations which constitute the progressive history of 
our planet. 

Thus assisted by the determinations of as- 
tronomy, geology, chemistry, and meteorology, as 
regards the general constitution of the globe, phy- 
sical geography proceeds to describe and explain 
its superficial appearance and conditions, and 
those, again, as influencing the life and distribu- 
tion of the plants and animals by which it is 
peopled. Before entering, however, upon these 
interesting but complicated details, it will be 
necessary to explain the principal terms and tech- 
nicalities usually employed by geographers. 

GEOGRAPHICAL TERMS. 

The direction from which the earth moves in its 
daily rotation is called the West; that towards 
which it moves, the East; the point which is on 
the right hand of one standing with his back to 
the east is called the North; that on the left hand, 
the South. The imaginary line on which the earth 
turns is called the Axis; its termination towards 
the north is known as the North Pole; that to- 
wards the south, the South Pole. The early culti- 
vators of geography, dwelling on a part of the 
earth nearer the north than the south pole, sup- 
posed the former to be uppermost, though, in 
reality, such ideas as upper and under do not 
belong to astronomy; and it is for this reason 
that in globes and maps the northern part is 
always placed at the top, the east being towards 
the right, and the west towards the left hand, with 
the south at the bottom. Hence also the term 
high latitudes, applied to places lying far north. 
Exactly between the two poles, and consequently 
dividing the earth into two equal portions, is a line 
called the Equator; all north and south of which 
are respectively called Northern and Southern 
Hemispheres or Half-spheres. In the same way, 
an encircling line, at right angles to the equator, 
divides it into Eastern and Western Hemispheres. 
The circuit of the earth, both in its girth between 
east and west, and between north and south, is 
divided into 360 parts, called degrees, each degree 
being equal to about 69^ British miles. At the dis- 
tance of 23^ oi these degrees from the equator, in 
both directions, are two parallel lines called the 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Tropics, because at these distances from the equa- 
tor the sun turns in his annual path ; they are known 
respectively as that of Cancer and that of Capri- 
corn, from constellations situated in a correspond- 
ing part of the sky. At the same distance from 
each pole is a parallel line — that on the north 
being styled the Arctic, and that on the south, the 
Antarctic Circle. The space between the tropics 



II0«T1| 






CsfUMP \ 


I Zlqua.tor 


t.^ \ 


\ "Tr»m» of 


Capri»»m 1 


\ jtiUarMe 


J 

CinU / 




_^^ 



SOUTH POLK 



is called the Torrid Zone, because the sun, being 
always vertical in some part of that space, pro- 
duces a greater degree of heat than is felt in 
regions where his rays strike more obliquely. The 
spaces between the tropics and the Arctic and 
Antarctic Circles are styled the Temperate, and 
the spaces within these latter circles, the Frigid 
Zones. Lastly, a line, which cuts the equator 
obliquely, touching upon opposite points of the 
tropics, is called the Ecliptic; it properly belongs 
to the sphere of the heavens. A series of lines 
drawn from pole to pole over the earth's surface, 
and cutting the equator at right angles, are called 
Meridians, from the Latin meridies, mid-day. 
Every place upon the earth is supposed to have 
one of these passing through it, although it is 
usual to describe only twenty-four upon the sur- 
face of the terrestrial globe. When any of these 
is opposite the sun, it is then mid-day, or twelve 
o'clock, with all the places situated on that meri- 
dian ; and consequently midnight with those on 
the opposite meridian, on the other side of the 
earth. 

The exact situation of a place upon the earth, 
or its latitude and longitude, is determined by 
means of these circles. They are all divided, as 
already stated, into 360 parts, which parts are 
called degrees J these degrees again into 60 equal 
parts, called minutes ; the minute into 60 others, 
called seconds J and so on. They are usually indi- 
cated by certain signs — thus, 8° 5' 7", is 8 degrees 
5 minutes 7 seconds. The latitude of a place is 
its distance measured in that manner from the 
equator. If it lies north of that line, it is in north 
latitude; if south of it, in south latitude. There 
being only 360 degrees in the circumference of the 
earth, and the distance from the equator to either 
of the poles being only a fourth part of it, a place 
can never have more than 90 degrees of north or 
south latitude. The longitude of a place is the 
distance of its meridian from another, which is 
called the first meridian. The first meridian is 
quite arbitrary, and it is a matter of indifference 
through what' point we draw it, provided it be 
settled and well known which one we adopt, so as 
to prevent mistakes. In Germany, the island of 

52 



Ferro is generally adopted ; in France, the obser- 
vatory of Paris ; and in England, that of Green- 
wich. Longitude is reckoned either east or west 
of the first meridian ; and 180 is therefore the 
utmost degree of longitude. Some geographers, 
however, reckon longitude all the way round the 
globe. From the meridians all tending to a point 
at either pole, the degrees of longitude necessarily 
decrease as we approach these points from the 
equator. 

Besides these terms and technicalities, which 
refer to the earth as a whole, there are others 
employed to designate its separate portions of 
land and water. Thus of the land, a continent 
is any vast region uninterrupted by seas ; an 
island, any smaller portion surrounded by water ; 
a peninsula, a portion nearly surrounded by water ; 
an isthmus, the narrow neck which connects a 
peninsula with the mainland ; a cape, promontory, 
or headland, a point of land jutting out into the 
sea. As to the water, a large uninterrupted extent 
of sea is called an ocean; smaller portions are 
known as seas; a bend of the sea into the land, a 
bay ; a deeper indentation, a gulf; a narrow strip 
of sea, a strait or channel; and where the sea 
stretches inland to receive the waters of some 
large river, it is termed z. firth or estuary. Refer- 
ring to the surface of the land, without any refer- 
ence to water, extensive flats are known as plains, 
steppes, pampas, &c. ; smaller ones as valleys, 
straths, and dales; elevated land is spoken of as 
rising into hills, or, still higher, into mountains; 
and level elevated tracts are known by the name 
of table-lands or plateaux. Running water makes 
its appearance in springs, many of which conjoined 
form streams, and streams rivers; and where 
these become stagnant, and spread out into inland 
sheets, they take the name of lakes. The bound- 
ing-line of land and water is termed the shore, and 
the land bordering on the sea in any place is 
generally spoken of as the coast or sea-board. 

DISTRIBUTION OF LAND AND WATER. 

To exhibit the earth's surface at one view, it is 
usual to map it into two halves or hemispheres — 
the Eastern comprehending the one great conti- 
nent of the Old World, or that known to the 
ancients ; and the Western, or New World, discov- 
ered and explored since the close of the fifteenth 
century. To these, modem geographers add a 
third — namely, Oceania, or the Maritime World, 
partly situated in both hemispheres, and com- 
prising Australia and the vast groups of islands 
which stud the Pacific Ocean. It will be seen at 
one glance that the sea and land are very unequally 
distributed — that they preserve no regularity of 
outline or form — and that either is placed indif- 
ferently as to position, on the earth's surface. 
Many fanciful conjectures have been offered tO' 
account for the configuration of the existing con- 
tinents, but none of them seem to have any founda- 
tion in fact 

Though we are thus unable to account for the 
present relative arrangement of sea and land, there 
is one determining principle sufficiently clear — 
namely, that so long as the same quantity of water 
remains on the globe, a fixed amount of cubic 
space will be required to contain it. If the differ- 
ence between the elevations and depressions of 
the solid crust be small — in other words, if the 



PHYSICAL GEOGRAPHY. 



hollows in which lakes and seas are spread out be i the climate more genial and uniform ; and, extend- 



shallow — their waters must extend over a greater 
superficial space; and if these hollows be deep, 
the waters will occupy less extensive areas. The 
operation of this principle should be borne in 
mind ; for, if the inequalities of the land were 
generally less, the waters would occupy larger 
spaces, and this more extended area of shallow 
water would act in various ways. It would render 



ing a greater surmce to the evaporating power of 
the sun, rains and-atmospheric moisture would be 
more prevalent. These, again, would influence 
the amount and kind of animal and vegetable life 
on dry land ; while the shallow waters themselves 
would be more productive of life — it being a well- 
known fact that marine plants and animals flourish 
only at limited depths. 




The proportion of dry land to water, as at pres- 
ent known, is about one to three — that is, nearly 
three-fourths of the whole surface of the globe may 
be assigned to water. Reckoning the entire area 
of the globe at 197 million square miles, the land 
is computed to occupy about 52 millions, leaving 
145 millions for sea. The land is far from equally 
distributed over the globe ; the greater part of it 
lies north of the equator. * If,' says Professor 
Ansted, * a p)erson, stationed vertically over the 
town of Falmouth in England, could see half the 
globe, he would see more than 49 out of the 52 
millions of square miles of land, or about an equal 
surface of land and water. If, however, he were 
perched equally high above New Zealand, he 
would see 96J millions of square miles of water, 
and less than two millions of square miles of land.' 
To render this unsymmetrical protuberance of the 
land consistent with the right balancing of the 
globe, it has been assumed that the rocks in the 
water hemisphere may be heavier than those in the 
other, arising either from their containing more 
metal or being more compact 

CONTINENTS AND ISLANDS. 

The continuous masses of land large enough to 
deserve tlie name of continents are only three in 
number— the Eastern Continent, or Old World j the 
Western Continent, or New World ; and the South- 
em Continent, or Australia. By much the largest is 
the Eastern Continent ; Europe, Asia, and Africa 
are, strictly speaking, not separate continents, but 
divisions or lobes of this vast tract North and 
South America, in like manner, are the two 



divisions of the Western Continent The areas of 
the three continents, with the adjacent islands, in 
round numbers of millions of miles, are as follows : 

Old World, or Eastern Continent 31,330,000 

Europe 3,724,000 

Asia 16,152,000 

Africa 11,354,000 

New World, or Western Continent 15,000^000 

North America 8,200,000 

South America 6,800,000 

Southern Continent, or Australia 4,633,000 

The outline and disposition of the three conti- 
nents are as diverse as can well be conceived. 
The great mass of the Old World lies north of the 
equator, with its main axis ranging from north- 
east to south-west. The western continent runs, 
in its longest direction, nearly from north to south, 
and has considerably more of its area, in propor- 
tion, to the south of the equator than is the case 
in the other continent Australia, again, is wholly 
in the southern hemisphere, has its greatest length 
from east to west, and is of a compact oblong 
shape, while the other two continents are exces- 
sively irregular and deeply indented. The Old 
and New Worlds ag^ee in one remarkable circum- 
stance; nearly all the projecting portions point 
southwards, and are mostly of a triangular shape. 
This is seen, in the Old World, in Kamtchatka, 
Corea, Malacca, Hindustan, Arabia, Southern 
Africa, Italy, Greece, Spain, Scandinavia; and in 
the New, in Greenland, Alaska, California, Florida, 
and South America. Retaining the generally 
acknowledged divisions, let us glance at their 
respective positions and superficial characteristics 
as influencing the vitality of our planet 

Europe — lying almost wholly within the northern 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



temperate zone, diversified by a happy blending of 
mountain and plain, marked by no geographical 
feature on a scale so large as to give to its surface 
the character of monotony, and surrounded and 
intersected by seas which greatly influence its cli- 
mate — affords, in proportion to its area, a habitat 
to a more varied and highly developed existence 
than any other quarter. Asia, situated partly 
within the torrid, temperate, and frozen zones, 
and presenting an area almost five times that of 
Europe, exhibits every species of geographical 
diversity. With such a variety of character, it is 
impossible to treat of it as a whole, and conse- 
quently geographers divide it into five well-marked 
regions — namely. Central Asia, consisting of a 
series of ascending plateaux, diversified by moun- 
tain-ridges of stupendous height, and intersected 
by narrow valleys ; Northern, including the whole 
of the continent north of the Altai Mountains — a 
flattish region traversed by large rivers, bleak and 
barren, suffering under an intense cold, thinly 
peopled, and almost physically incapable of im- 
provement ; Eastern — upon the whole a low-lying 
and somewhat arid region, though traversed by 
several of the largest rivers in the world, and 
occasionally diversified by spurs from the central 
table-heights ; Southern, including the two penin- 
sular projections of India within and without the 
Ganges — decidedly the finest region of the conti- 
nent, diversified by minor hill-ranges and well- 
watered valleys, enjoying a high, though not an 
oppressive temperature, having only a rainy season 
for its winter, and, except during long drought, 
presenting in every district an unfailing verdure ; 
and, lastly, Western Asia — from the Indus west- 
ward and north to the Caspian — which, with a few 
minor exceptions, may be said to consist of high 
sandy plains, studded with salt-lakes, very inade- 
quately watered by rivers, and on the whole a 
hot and arid region. A continent marked by such 
a diversity of surface and climate, presents an 
appropriate field for the exhibition of almost every 
form of vitality known in the other continents; 
and thus has belief ever pointed to it as the cradle 
of organic existence. Africa, the next great divi- 
sion of the Old World, is almost entirely insular, 
the isthmus connecting it with Asia being only 
seventy-two miles across, of no great elevation 
above the sea-level, and even in part occupied by 
lakes and salt-marshes. It is only a few years 
ago that little was known regarding the physical 
construction of Africa beyond a limited strip 
around the coast, and a few tracks across the 
Great Desert of the north. Thanks to the adven- 
turous explorations of recent travellers, we now 
have a tolerable notion of its general features. 
One of these features is an almost continuous 
range of mountains girdling the continent round, 
leaving a belt of lowlands of from 50 to 300 miles 
broad between them and the coast. In the tri- 
angular part of the continent, south of Cape 
Guardafui and the Gulf of Guinea, the interior 
consists of an elevated plateau variegated by 
mountain tracks, river-valleys, and depressions 
containing great lakes; the whole abounding in 
multiform vegetable and animal life. North of 
this plateau the interior consists of the compara- 
tively low-lying and fertile track known as Nigritia 
and the Great Desert or Sahara. The isolation 
of Africa, its intertropical position, and its general 
configuration, must stamp it with vital peculi- 
54 



arities ; and yet its connection with Asia on the 
one hand, and its proximity to Europe on the 
other, offer numerous facilities to the interchange 
of vegetable and animal species. Thus the south- 
ern and northern sea-board of the Mediterranean 
present many similar forms ; and the Flora and 
Fauna of Egypt and Nubia are identical in many 
instances with those of the adjoining tracts of 
Arabia. 

Turning now to the New World, we find also 
the two Americas so slenderly attached by the 
narrow rocky Isthmus of Panama, which at one 
part is little more than eighteen miles across, that 
they may safely be regarded as separate and dis- 
tinct continents. This separation is rendered still 
more decided by the irregular character of the 
isthmus and the adjoining high table-land of 
Mexico, which form an almost impassable barrier 
to the migration- either of animal or of vegetable 
races. South America lies chiefly within the 
tropics, a third part or less stretching southward 
into the temperate zone ; its superficies is broadly 
marked by mountain and plain, exhibiting along 
the entire western coast a flat arid region, from 50 
to 100 miles in breadth ; then rising boldly up into 
the Andes, which stretch along its whole length, 
and present a rugged irregular region of variable 
breadth ; and ultimately falling away to the north 
and east in the llanos of the Orinoco, the plains of 
the Amazon, and the pampas of La Plata. Nor 
are its physical features more broadly marked 
than the plants and animals by which it is peopled, 
these exhibiting typical peculiarities only next in 
degree above those of the somewhat anomalous 
continent of Australia. The problem of the north- 
west passage being now solved, Greenland and a 
number of islands lying west of it might be con- 
veniently erected into a new geographical division. 
Following, however, the usual course of including 
these regions, the area of the known continent of 
North America may be stated at 8,200,000 square 
miles — the great mass of which lies within the 
northern temperate zone. The general physical 
characteristics of the continent are remarkable for 
the magnitude of the scale upon which they are 
presented — the plains, lakes, and rivers being 
superior to those of all other countries. Though 
lying chiefly within the temperate zone, its south- 
em and northern regions are respectively placed 
under tropical and arctic influences ; and thus it 
presents in some measure the threefold variety of 
Fauna and Flora which characterises the greater 
continent of Asia. This greater diversity of climate 
renders it less peculiar in its living forms than the 
sister continent, at the same time that its prox- 
imity to Asia — being separated by Behring's Strait, 
which is only thirty-six miles broad — renders the 
immigration of Old- World species by no means 
improbable. 

In estimating the comparative adaptability of a 
land as the habitation for man, an important ele- 
ment is the extent of its coast-line compared with 
its area. The more irregular the shape of the 
land, and the more it is broken into by gulfs and 
bays, the more are the inland parts brought into 
proximity to the great highway of intercourse and 
civilisation. Europe is so indented with seas and 
gulfs, that it has a coast-line of 20,000 miles, while 
the same area might be contained in a regular 
figure of 6000 miles' circuit. Had it had an outline 
of this kind, it would hardly have been, as it is. 



PHYSICAL GEOGRAPHY. 



the habitat of the most advanced races. The fol- 
lowing table exhibits the number of square miles 
of area to one mile of coast in the several large 
divisions of land, thus affording a measure of the 
comparative accessibility of the interior : 

Europe i57 ^- miles of area to x mile of coast. 

Asia 52S It ir 

Africa 738 ?i II 

North America 366 n u 

South America. 440 n 11 

Australia 340 n 11 

The insular portions of the globe are not less 
worthy of notice than the continents themselves. 
We find them sometimes solitary, oftener collected 
into groups or archipelagoes : in some cases they 
are little more than low sand-banks, ledges of 
rocks, or coral reefs ; and in others — rising to a 
considerable elevation above the surface of the 
water, and spreading to a considerable extent — 
they present in miniature all the features of the 
continents to which they belong. They are often 
the summits of submarine mountain-chains, and, 
as such, are intimately connected with each other 
and with the neighbouring mainland. Many of 
them are evidently the production of volcanic forces 
— the dawn of new continents emerging from the 
waters, as others are the gradually submerging relics 
of former terrestrial regions. The most important 
island-groups are the British, Japan, Philippine, 
and East Indian in the eastern hemisphere ; and 
the West Indian and Polynesian in the western. 
The largest individual islands (regarding Australia 
as a continent) are — Borneo, with an area of about 
280,000 square miles ; Madagascar, 234,000 ; New 
Guinea, whose outline is yet imperfectly known ; 
Sumatra, 177,000; Niphon, 109,000; Great Bri- 
tain, 90,000 ; Nova Zembla, 25,000 ; Newfound- 
land, 40,000; Cuba, 43,400; and Iceland, 40,000 
square miles. 

Islands, we have said, are either connected with 
existing continents, are portions of former conti- 
nents now submerged, or are new and independent 
elevations. Thus, if an island is of the same 
geological formation with the adjoining mainland, 
we must regard it either as a portion separated by 
depression, or as a belated portion only rising into 
dry land. In either case, we are bound to con- 
sider it in all its relations — vital as well as physical 
— as belonging to the adjacent continent. Again, 
islands of totally different formation from that of 
the nearest continent may in most cases be re- 
garded either as relics of former lands, or as new 
lands rising into day ; and we are not to be startled 
at the fact of their exhibiting — like Australia — 
races of plants and animals altogether peculiar. 

Such is a brief glance at the partition of the dry 
land (so far as it is known) into continents and 
islands — a partition which exercises an all-import- 
ant influence over organic existence, and which, 
after all, is dependent on very minute geological 
operations. A general elevation of the solid crust 
in the eastern hemisphere, for example, would 
connect Britain with the continent of Europe, the 
Lofoden Islands with the Scandinavian peninsula, 
enlarge the connection between Asia and Africa, 
elevate the Sunderbunds of the Ganges into a vast 
plain, the Laccadive and Maldive reefs into exten- 
sive islands, and the bed of the Yellow Sea into an 
alluvial plain. Equally important results depend 
upon the relative positions of the continents and 
islands. Had South America, unaltered in a 



smgle square yard, Iain parallel with, instead of 
crossmg, the equator, or had Africa been inter- 
sected by seas, as Europe is, it requires no stretch 
of imagination to conceive the radical difference 
which their Flora and Fauna would have pre- 
sented. As regards man, and the highest aim 
of creation — the civilisation of man— the present 
arrangement is of the first importance. The theatre 
of his operations all arctic, and he would never 
have risen above the condition of the Laplander 
or Esquimaux ; all antarctic, and behold his con- 
dition in that of the miserable Fuegian ; all tropi- 
cal, and see him in a state of languid, enervated, 
semi-civilisation ; while balanced as conditions 
are, see his progress mainly in one broad zone, 
where Chinese, Indian, Persian, Chaldean, Syrian, 
Egyptian, Greek, Roman, Frank, and Anglo-Saxon 
have successively or simultaneously figured in the 
march of improvement 

MOUNTAINS AND TABLE-LANDS. 

As elevation above the waters of the ocean is 
the origin of the dry land, so its most prominent 
features are those peculiar upheavals known by the 
name of hills and mountaitis. The theory of their 
upheaval belongs to Geology ; but according to 
their character, so is that of the regions to which 
they belong, generally speaking, determined. They 
subserve numerous and important purposes in 
nature. Rising into regions of perpetual ice, they 
serve, in hot climates, to temper the air with the 
breezes generated around their heights ; they are 
the reservoirs of rivers, supplying the shrinking 
streams, in the dry seasons of the lower countries, 
with copious torrents from their melting snows; 
they are in most instances the storehouses of the 
richest minerals ; they increase and diversify the 
surface of the earth ; and, by presenting impassable 
barriers between opposite regions, they give variety 
and richness to animal and vegetable life : we say 
impassable barriers, for the broadest seas are not 
half so effective in obstructing the dispersion of 
vegetable and animal life as lofty snow-clad 
mountains. 

Isolated mountains of great height are of rare 
occurrence, and when they do appear, are usually 
active or recent volcanoes. Hills and mountains, 
whether rising to the height of 1000 or 20,000 feet, 
generally appear in chains or ranges, consisting 
either of one central chain, with branches running 
off at right angles, or of several chains or ridges 
running parallel to each other ; and in both cases 
often accompanied by subordinate chains of minor 
elevation. Several chains constitute what is called 
a group; and several groups, a system. The 
relative ages of mountain-chains appertain more 
especially to the province of the geologist ; but 
with their epochs is connected their physiognomy 
or contour, a subject eminently interesting to 
the geographer. So persistent is the contour of 
mountains, whether associated with the older or 
more recent formations, that the practised eye of 
the geologist can generally determine at a glance 
the era of their upheaval The bold, but bald and 
massive heights of a granitic mountain differ widely 
in aspect from the abrupt and splintery crags 
and pinnacles of the older stratified formations ; 
while the rounded, undulating, and terraced out- 
line of the secondary trap-hills distinguishes them 
at once from the conical crateriform heights of the 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



tertiary era. Nor is it in appearance alone that 
these distinctions are interesting ; the cold barren 
subsoil of a granitic district, altogether independ- 
ent of elevation, diflfers as widely in its vegetable 
exhibitions from those of a fertile and congenial 
trap, as a cultured garden does from a moorland 
wild. 

Respecting the classification of mountains, 
various plans have been adopted by continental 
writers ; but most of them are objectionable, as 
involving geological theories : we shall adhere 
to that simpler arrangement which takes into 
account merely their geographical position and 
connection. Those of Europe have been clas- 
sified into a number of systems, some of which 
are continental, others insular. Laying aside 
minutias, the following seem to be distinct and 
natural : i. The Hesperian, embracing the moun- 
tain-ridges of the Spanish peninsula — all of which 
maintain a wonderful parallelism in position, as 
well as unity of character, and whose extreme 
culminating point is Maladetta, in the Pyrenees, 
Ii,i68 feet. 2. The Gallic system, including all 
the hilly eminences in France which lie to the 
north of the Garonne, west of the Rhone, and south 
of the Rhine. None of these are of great age, or 
of great elevation, the highest being a peak of the 
Plomb de Cantal, in Auvergne, 61 13 feet. 3. The 
Alpine system, embracing all those ridges and 
branches which radiate from the great Alpine 
range of Switzerland, such as the Maritime, 
Cottian, Pennine, Rhetian, Noric, and other 
Alps ; the Apennines in Italy, and the Balkan or 
Haemus group in Turkey. The highest or cul- 
minating point is Mont Blanc, in Switzerland, 
15,732 feet. 4. The Hercynio-Carpathian system, 
including all the mountains and eminences compre- 
hended between the Rhine, Dnieper, and Danube, 
the plains of Northern Germany and Western 
Poland. The highest point in this system is Lom- 
nitz, in the Central Carpathians, upwards of 8000 
feet 5. The Scandinavian, a system of the highest 
antiquity, embracing the well-defined chains of 
Norway, Sweden, and Lapland, the extreme height 
of which does not much exceed 8000 feet 6. The 
Ural system or chain, which forms the boundary- 
line between Europe and Asia, and rises in its 
highest part to between 5000 and 6000 feet. 
Lastly, the Britannic system, consisting of a 
number of detached chains, as the Grampians, 
Cheviots, and Welsh mountains, the highest point 
of which is Ben Nevis, in Inverness-shire, 4406 
feet. All of these systems, as axes of elevation, 
have long ago become fixed and permanent ; none 
of them has for the last two thousand years shewn 
symptoms of volcanic activity : Hecla, Vesuvius, 
and Etna, the only active volcanoes in Europe, 
seem to point to future upheavals. 

The mountains of Asia may be all traced from 
that vast central plateau already adverted to, 
which forms, as it were, the nucleus of the con- 
tinent. Omitting ranges of minor altitude, we 
may enumerate — the Altai, an Alpine girdle 
(greatest height 12,790 feet), running along the 
50th parallel of latitude from the 84° of longitude 
to Lake Baikal, and continued eastward in the 
Daurian system and Stannovoi mountains, which 
are supposed to stretch to Behring's Strait ; the 
Khin-gan range, bounding the Desert of Gobi on 
the east, but of unknown altitude ; the Thian- 
shan and Kuen-lun, two ranges beginning in the 

56 



west of Chinese Tartary, and running eastward — 
the former about the parallel of 42°, the latter 
about 36°— into China ; attaining in some summits 
a height of upwards of 20,000 feet, and remarkable 
as containing active volcanoes at a distance of 
1500 miles from the sea ; the great Himalaya 
mass, extending about 1500 miles in length, and 
from 100 to i»D across, rising from the Indian 
side by stages of 4000, 8000, and 11,000 feet 
to a mean elevation of 18,000 or 20,000 feet, 
attains in several peaks the height of about 
25,000, in Dhawalagiri 26,826, in Kinchinjunga 
28,156, and in Mount Everest 29,000 — probably 
the greatest elevation on the globe ; the Hindu 
Kusk, with their southern ramifications, which 
may be regarded as prolongations of the Hima- 
laya ; and, lastly, the Tauro-Caucasian system, 
diversifying the west of Asia with numerous 
ridges and peaks, the highest of which are Elburz, 
18,493 feet, and Demavend, 21,000. In connection 
with these systems and ridges are active volca- 
noes, as in Kamtchatka, Japan, the Thian-shan 
ranges, &c. 

The mountain-systems of Africa are as yet only 
partially known. The hills of Cape Colony rise 
from Table Mount, 3582 feet, to the summits of 
the Nieuveldt and Snieuveldt mountains, in the 
north of the colony, which are estimated at 7000- 
10,000 feet ; the spaces between the ranges being 
broad elevated terraces or karoos, connected by 
shrubby kloofs or valleys. Beginning with Cape 
Colony, one vast table-land, the greatest on the 
globe, occupies the south of the African continent, 
stretching on the east as far north as Nubia. The 
mountain-ranges seen running parallel with the 
east coast form the border of this table-land ; 
the highest of them yet seen is Kilima-Njaro, 
between 3° and 4° south latitude, estimated at 
20,000 feet. The Abyssinian mountains form a 
terminating cluster to the range, reaching in the 
Abba Jared, at the extremity of the table-land, the 
height of 15,000 feet. The Cameroons, on the 
west, are above 13,000 feet ; some of the summits 
around the great equatorial lakes in the interior 
rise to 10,000, but none of them, apparently, into 
the region of snow. On the north, between the 
Sahara and the Mediterranean, the Atlas system 
is well defined, and here an elevation of 11,400 
feet has been ascertained. 

The mountains which traverse South America 
may be ranked under two systems — the Cordillera 
of the Andes, and the Mountaitis of Brazil. The 
former, in several parallel chains, extend along 
the western edge of the continent from the Strait 
of Magellan to the Caribbean Sea, in many places 
spreading out over a breadth of several hundred 
miles, embracing lofty table-lands, containing 
mountain lakes, and everywhere intersected by 
steep narrow ravines and passes. A remarkable 
feature of the Andes is that the parallel ranges 
frequently come together, forming lofty table-lands 
called knots. At Popayan, the main chain divides 
into three ridges, one of which, shooting off to the 
north-west, passes into the Isthmus of Panama ; 
a second separates the valleys of the Cauca and 
Magdalena ; and a third, passing off to the north- 
east, separates the valley of the Magdalena from 
the plains of the Meta. The most elevated portion 
of the system is the Bolivian Andes, from south 
lat 21° to 14°, numerous summits of which rise to 
13,000-22,000 feet. The highest peak of the 



PHYSICAL GEOGRAPHY. 



system is in Chili, where Aconcagua is 22,300 
feet — perhaps the highest volcano in the world ; 
Chimborazo, in the equatorial Andes, is 21,424, 
Altogether, the Andes present a most magnificent 
spectacle to the voyager on the Pacific ; the snow 
which permanently covers their lofty summits, 
even under the burning sun of the equator, con- 
trasting beautifully with the deep blue of the sky 
beyond ; while occasionally another contrast is 
exhibited in vast volumes of smoke and fire, 
emitted from some of the numerous volcanoes 
which stud the entire range. The Brazilian moun- 
tains occupy a great breadth of country, but 
seldom exceed an elevation of 6000 feet. 

The chief mountain-system of Central and 
North America may be considered as a con- 
tinuation of the Andes of the south, the whole 
forming, as it were, the backbone of the New 
World, and extending from Cape Horn to the 
Arctic Ocean, a distance of nearly 10,000 miles. 
The Cordilleras of Central America, or Mexican 
Andes, as they are sometimes called, extend from 
the Isthmus of Panama to the north of Mexico. 
They spread themselves, for the most part, from 
sea to sea. At Panama, where the range is 
crossed by a railway, the elevation is under 300 
feet ; but it increases towards the north. The 
greater part of Mexico consists of magnificent 
table-lands from 5000 to 9000 feet high, girt and 
intersected by mountain-ranges, with peaks — 
several of them volcanic — rising above 17,000 
feet. Within the United States and British 
America, the system is known by the general 
name of the Rocky Mountains. It consists of 
several parallel ranges running in the general 
direction of the Pacific coast, and between that 
coast and the head-waters of the streams that flow 
into the Mississippi, and extending over a tract 
1000 miles broad from east to west. The eastern 
range or axis, which forms the main water-shed 
between the basin of the Mississippi and the 
Pacific, rises in Fremont's Peak to 13,570, and 
farther north, in Mount Brown, in British America, 
to 16,000. The western or Maritime range attains, 
in the Sierra Nevada of California, a height of 
14,000 ; and in Mount St Elias, on the coast, in 
lat. 61°, a height of 17,800. The AUeghanies or 
Appalachians, on the east side of the continent, 
extend in parallel ranges, with valleys between, 
from Alabama to Main ; the highest summit of 
the system is Mount Washington, in New Hamp- 
shire, 6634 feet. 

In Oceania we have several minor groups and 
ranges ; but the principal elevations are in 
detached volcanic heights, the index-fingers, as it 
were, to future mountain-systems. In Malaysia, 
the highest known point is Mount Ophir, in 
Sumatra, 13,850 feet. The east coast of Australia 
is bordered by a range of no great elevation ; but 
a backbone runs through the islands of New 
Zealand, near the west coast, attaining a height 
in some peaks of 10,000 to 12,000 feet. The 
highest points in Polynesia are the active vol- 
canoes of Mauna Kea and Mauna Loa, in Hawaii, 
each about 14,000 feet. 

Such are the more prominent mountain-systems 
as known to geography. Those who regard them 
as mere ridges, rising on one side, and descending 
as abruptly on the other, and at most intersected 
by a few narrow passes, gorges, and ravines, form 
a very erroneous conception of the physical con- 



tour of the globe ; for, so far from this being the 
case, most of these systems are but the escarp- 
ments or ramparts of elevated expanses known 
as plateaux or table-lands, which form in some 
instances the nucleus of continents, and the source 
from which the rivers of such continents flow. 
Thus, on examining the map of Asia, it will be 
seen that all the rivers flow— north, east, south, and 
west — from the central region, which in reality 
forms a succession of remarkable plateaux. These 
plateaux may be termed the Persian, which ranges 
from 3000 to 6000 feet above the sea ; the Mon- 
golian, at an elevation of from 8000 to 12,000 
feet ; and that of Tibet, which reaches 1 7,000. 
There are some masses of this kind in Europe, 
but of comparatively small extent — as the central 
part of Spain, which is about 2200 feet in height ; 
and the Swiss table-land, between 3000 and 4000 
feet. The elevation of the great South-African 
plateau seems to be highest towards the east side. 
In South America, the city of Potosi, in Bolivia, 
is situated in the elevated valley of Desaguadero, 
at 13,600 feet above the sea-level ; and the plateau 
on which Quito stands has an elevation of 9000 
feet. One of the most noted table-lands is that of 
Mexico, not less remarkable for its elevation than 
for its extent. 



EARTHQUAKES AND VOLCANOES. 

These are rather agents than effects— rather the 
cause of geographical diversity than geographical 
features themselves ; and in this respect belong 
more properly to the province of geology : still, 
as much of the superficial irregularity is the direct 
result of their operations, and as it is often 
impossible to separate cause from effect, it will 
be necessary here to give them some further con- 
sideration. 

Volcanoes affect the external features of the 
earth chiefly by the matter they eject from its 
interior. By the discharge of lava, loose stones, 
scoriae, fine dust or volcanic ash, and other 
materials from these vents, multitudes of isolated 
conical mountains have been formed ; valleys 
have been filled up by the lava-streams, and 
woods, villages, and cattle have been buried. 
The immense volumes of steam generally dis- 
charged during an eruption condense into rain, 
and mixing with the ashes, form torrents of mud, 
little less destructive than the rivers of lava. A 
mud avalanche from Vesuvius overwhelmed the 
ancient Roman cities of Pompeii and Herculaneum 
in 79 A.D. As an example of the enormous 
masses of material thus poured out from the 
interior of the earth, we may cite Etna in Sicily. 
It reaches a height of nearly ir,ooo feet, with a 
circumference of about ninety miles, and is com- 
posed entirely of lava and ashes thrown out from 
many different points around the central cone. 
There are several hundreds of volcanoes now in 
activity, and there is evidence that they once 
existed in many places where they have long been 
extinct. In Auvergne, in the centre of France, 
there are lofty mountains of lava, and numerous 
cones of loose cinders rise into conspicuous hills, 
each with its crater, while congealed streams of 
lava can be traced down the plateau into the 
valleys. Yet all is cold and still, and has been so 
for unknown ages. Sheets of lava are still con- 
spicuous in the British Islands ; but they have 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



been so long exposed to the wasting of the ele- 
ments, that no actual crater can now be traced. 
Volcanoes for the most part occur in lines, and 
not far from the sea ; partly along the margins of 
the great continents, partly in chains of oceanic 
islands. The most remarkable example of the 
marginal arrangement is seen in the long chain of 
volcanic vents that studs the western border of 
America from Tierra del Fuego to Mexico. Of 
insular volcanoes the most numerous and energetic 
occur in the Indian Archipelago — Sumatra, Java, 
and the adjacent islands. Along the island of 
Java there runs a band of not less than forty- 
five volcanoes, most of which have been seen in 
eruption. 

But the forces, whatever they are, that produce 
volcanoes and earthquakes do not always act in 
this violent paroxysmal way. They are constantly 
producing movements and changes on a vastly 
greater scale than anything resulting from earth- 
quakes and volcanoes, but so gently and insensibly, 
that it is only by the results which they bring 
about in a long course of years that we can detect 
their operation. Without shaking or rending the 
earth, they succeed, in the end, in elevating vast 
tracts of land above the sea, or in depressing them 
beneath it. The raised beaches which form so 
marked a feature in the scenery of many parts 
of the coasts of the British Islands, are evident 
proof of such a gradual upheaval The Scandi- 
navian peninsula, except a part of its southern 
end, is even now slowly rising ; in some districts, 
at the rate of two or three feet in a century. But 
the most marked elevation of a continuous kind is 
that which is taking place along the western coasts 
of South America. Evidences of the opposite 
movement — a gradual sinking of the land — are 
also abundant. The extreme south of Sweden is 
undergoing sensible depression ; and submerged 
forests on several parts of the British coasts point 
to a like operation. The most striking proof, 
however, of subsidence of the earth's crust is fur- 
nished by the coral islands of the Indian and 
Pacific Oceans. The characteristic form of the 
coral island is a ring of white rock enclosing a 
lagoon of still water, the walls of the ring rising 
for the most part perpendicularly from immeasur- 
able depths. Now the polypes that form these 
rocks can only live at a moderate depth, and it 
has been satisfactorily established that these ring- 
islands had their beginning in fringing reefs of 
coral such as are now seen off the shores of 
existing land. Let us suppose that one of these 
fringing reefs encircles some oceanic island, and 
that the sea-floor in that region is being slowly 
depressed. As the downward movement con- 
tinues, the corals keep building up the reef to 
about the level of the waves. In this way the 
space of water between the island and the coral 
ring is greatly increased, while, of course, the area 
of the island itself is correspondingly lessened. 
The downward movement continues — the island 
grows less and less, until its last mountain-top 
sinks beneath the sea. Over the submerged 
island there now stretches a smooth sheet of 
green water known as a lagoon. Encircling it 
is the circular reef of coral, or atoll, along the 
outer margin of which the restless waves of the 
ocean are ever surging. Soil gradually forms on 
the reef, seeds borne to it by the waves or carried 
by birds take root, and the ring of coral reef 

68 



becomes a habitable spot for man. Such is the 
history of the growth of the coral islands. They 
have been built round the summits of a sinking 
continent, over whose mountains and valleys the 
great ocean now rolls. 

What may be the nature of the force which 
produces these upheavals and subsidences, those 
quakings and eruptions, how it originated and 
how it is kept up, are questions to which, as yet^ 
no very definite answer can be given. It is clear, 
indeed, that heat plays a large part in producing 
these changes. The temperature of the earth is 
found always to increase as we descend into the 
crust ; and if the rate of increase which has been 
observed were to continue without any modi- 
fication, we should reach the melting-point of even 
the most refractory substances at the depth of a 
few miles. But, for reasons already given, the old 
notion that there is still a central liquid part in 
an incandescent state, with a thin crust over it 
liable to be shaken and brokeij. through by the 
commotions of the fluid interior, cannot now be 
held. 

That the interior of the earth, however, whatever 
be its composition, is intensely hot, is indicated 
by all the evidence we can gather on the subject. 
Some portions must be liquid, as is shewn by the 
discharge of fluid lava at a white heat from 
volcanic vents. There seems, indeed, to be good 
reason to believe that though the main mass of 
the interior may now be solid, there nevertheless 
exist within it large lakes or reservoirs of melted 
rock, and that volcanoes serve as the orifices of 
communication between these areas and the sur- 
face. When the water which is everywhere tra- 
versing the upper layers of the crust reaches these 
heated spaces, it is converted into steam, which 
exerts an enormous expansive force. The abund- 
ance with which steam is given off during vol- 
canic eruptions has long been familiar, and serves 
to indicate that steam may be the agent more 
immediately employed in forcing melted lava to 
the surface. During the changes which are in 
progress underneath, a mass of water will some- 
times be suddenly precipitated into an area of 
intensely heated rock, and its instant expansion 
will produce a sensible concussion or earthquake 
above ground. 

The constant transference of materials from the 
interior to the surface, whether by the action of 
volcanoes or by that of springs, must necessarily 
produce cavities within the crust When, for 
example, we contemplate such a mountain as 
Etna, and reflect that all its vast piles of lava, 
scoriae, and ashes have been abstracted from the 
interior of the earth, we see how real and important 
is this transference of material, and how easy it is 
to conceive of the formation of large hollow spaces 
beneath the surface. Again, the amount of solid 
material removed by springs, though it does not 
stand up before us as an enduring monument 
like Etna, is probably in reality greater in any 
one year over the whole globe, than all the lava 
and ashes which have been erupted by volcanic 
action during the same period. By some springs, 
such as those of a thermal kind, the quantity 
of these materials carried off in a single year 
would, if collected and rendered visible, make 
huge mounds or even small hills. Alike, there- 
fore, by the action of volcanoes and the subter- 
ranean circulation of water, cavities must be 



PHYSICAL GEOGRAPHY. 



produced within the interior of the earth. As 
these become enlarged, their roofs, from failure 
of support, will sometimes give way with a sudden 
collapse. Such is not impossibly the origin of 
many earthquake shocks. When we know that 
even on the surface the explosion of a powder- 
magazine sometimes gives rise to a tremor of the 
ground, which is felt at a distance of several miles, 
we may conceive how the collapse of one of these 
underground cavities, and the consequent rushing 
together of thousands of tons of rock, may send 
a pulsation for many miles through the elastic 
crust of the earth. 

The slow rising of some parts of the surface 
is accounted for by supposing that among the 
internal movements of the earth a great mass of 
rock may gradually have its temperature raised, 
and thus be expanded so as to push up the crust 
lying above it. In like manner, if the rock cools 
down, a slow depression of the overlying region 
will be the result. But without supposing an 
actual increase of temperature in any part, both 
upheaval and subsidence may be accounted for by 
the gradual cooling of the earth as a whole. As 
the nucleus shrinks in dimensions, the outer coat 
becomes too large for it, as it were, and has to 
accommodate itself by going into frumples, bending 
inwards in one part, and outwards in another. 
The inequalities on the surface of the globe have 
thus a similar origin to those on a shrivelled 
apple ; or, to vary the figure, continents and sea- 
beds, mountains and valleys, are the wrinkles that 
mark the aging of mother earth. 

PLAINS, VALLEYS, AND OTHER DEPRESSIONS. 

The plains, or level portions of the earth's sur- 
face, form a feature in its physical aspect equally 
important with that presented by its mountain- 
systems. The name, is given to extensive tracts 
whose surface in the main is level, or but slightly 
broken by elevations and depressions. They are 
found at all elevations above the sea, and of every 
degree of fertility ; from the exuberant tropical 
delta just emerging from the water, to the irre- 
claimable sterility of the desert of ever-shifting 
sand. 

The noblest of these expanses are the river- 
plains of the New World, drained by such waters 
as the Mississippi, the Amazon, and La Plata. 
Much of the Mississippi plain is rolling or undu- 
lating in its surface, well watered by minor rivers, 
exhibiting broad grassy prairies and extensive 
pine-forests. In South America we have first the 
low belt of country skirting the shores of the Pacific, 
from 50 to 100 miles in width, and about 4000 in 
length, fertile at its extremities, but in the middle 
sandy and arid ; next, the basin of the Orinoco, 
consisting of extensive plains called llanos, either 
destitute of wood, or merely dotted with trees, but 
covered during part of the year with tall herbage ; 
then the basin of the Amazon, a vast plain, 
embracing a surface of nearly ifxX),ooo square 
miles, possessing a rich soil and humid climate, 
and almost entirely covered with dense forests 
and impenetrable jungle-marshes by the river- 
sides ; and, lastly, the great Valley of the Plata, 
occupied chiefly by open plains called pampas, in 
some parts saline and barren, but in general 
clothed with weeds, thistles, and tall grasses. 
Next, in order of importance, is that section of 



Europe extending from the German Sea, throu<^h 
North Germany and Russia, towards the Ura' 
Mountains, presenting indifferently tracts of heath, 
sand, and open pasture, and regarded by geo- 
graphers as one vast plain. So flat is the general 
profile of this region, that it has been remarked, 
'it is possible to draw a line from London to 
Moscow, which would not perceptibly vary from a 
dead level!' Passing the Ural ridge, a plain of 
still greater dimensions stretches onward through 
Siberia, towards the shores of the Pacific. This 
region is of no great elevation, and, though diver- 
sified by occasional heights, consists chiefly of 
gravelly steppes, covered with coarse herbage, 
lakes, and morasses. In Africa, the northern and 
central portion, so far as explored, appears to be 
a vast expanse of Sahara, or sandy desert, broken 
at scanty intervals by oases of life and verdure. 

Certain minor tracts in these wide expanses 
receive distinctive designations. These are the ver- 
dant prairies of North America, already noticed, 
\}as. pampas and llanos of South America, the steppes 
of Asia and Northern Europe, the tundras or bog- 
marshes of Siberia, the grassy karoos of Southern 
Africa, the tangled jungles of India, the alluvial 
straths or dales of our island, and the low muddy, 
but gradually increasing deltas of such rivers as 
the Ganges, Nile, Niger, and Mississippi. To 
lesser flats and depressions — as valleys, glens, 
ravines, &c. — ^which give character to the land- 
scape of particular districts, our space will not 
permit us to refer. 

THE OCEAN. 

The ocean, though in fact a single mass of fluid 
resting in the hollows of the solid crust, sur- 
rounding the dry land on all sides, and indenting 
it with numerous bays and gulfs, is generally 
divided by geographers into the following great 
basins : The Pacific Ocean, 1 1,000 miles in length 
from east to west, and 8000 in breadth, covering 
an area of 50,000,000 square miles ; the Atlantic^ 
8600 miles in length from north to south, and 
from 1800 to 5400 in breadth, covering about 
25,000,060 square miles ; the Indian Ocean, lying 
between 40° south, and 25° north latitude, is about 
4500 miles in length, and as many in breadth, 
covering a surface of 17,000,000 square miles ; the 
Antarctic Ocean, lying round the south pole, and 
joining the Indian Ocean in the latitude of 40° 
south, and the Pacific in 50°, embraces an area — 
inclusive of whatever land it may contain — of 
30,000,000 square miles ; and the Arctic Ocean, 
which surrounds the north pole, and lies to the 
north of Asia and America, having a circuit of 
about 8400 miles. Besides these great basins, 
there are other seas of considerable extent, as the 
Mediterranean, covering an area of 1,000,000 
square miles; the German Ocean, 153,700; the 
Baltic, 134,900 ; the Black Sea, with its subordi- 
nate gulfs and branches, 181,000; but these and 
other minor sections will be more appropriately 
described when we come to treat of the respective 
countries (Volume II.) with which they are politic- 
ally as well as physically associated. 

Respecting the depth of the ocean, our know- 
ledge has recently become much more definite 
and certain, owing to improvements in deep-sea 
sounding. The floor of the North Atlantic, in 
particular, is nearly as well known as the most of 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



terra firma. Proceeding west from Ireland, the 
bottom descends in a succession of steps or 
terraces, sometimes of immense extent. The 
descent from one plateau to another is sometimes 
by steep cliffs 9000 feet deep. The greatest 
depth is some distance south of the great bank of 
Newfoundland, where there is a basin-shaped 
depression 1000 miles in length, with soundings 
of about 30,000 feet, or above five miles and a 
half. The bottom of the Pacific is less known : 
soundings of 40,000 feet have been obtained. 

The temperature of the sea, where it is not 
affected by currents from a warmer or colder 
region, necessarily corresponds to that of the air 
above it ; but this is true only of the water at 
and near the surface. In the Mediterranean, for 
example, the surface temperature ranges from 80° 
in summer to 54" or 55° in winter. But this 
excess of summer heating does not extend beyond 
a depth of 100 fathoms : below this, the tempera- 
ture of 54° or 55° is maintained constantly at all 
depths ; and this temperature is that of the crust 
of the earth in that region. In the Atlantic, in 
the same latitude, the temperature of the upper 
stratum of 100 fathoms does not essentially differ 
from that in the Mediterranean ; but at greater 
depths, the temperature sinks to 49°, 40°, 38°, 36°, 
and in some places to the freezing-point of fresh 
water, and even below it (29'6°). Recent obser- 
vations tend to shew that an almost glacial cold- 
ness prevails over the whole deep-sea bed in both 
Tiemispheres, extending even to the tropics. The 
cause of this phenomenon will be explained when 
we come to speak of the currents of the ocean. 

The sea consists of salt water, as already ad- 
verted to, and from its continual motion, under 
the influence of currents and waves, preserves, 
generally speaking, uniform saltness. Under 
special circumstances, however, we find the salt- 
ness increased, as by the excess of evaporation 
•over the fresh-water influx in the Mediterranean 
and Red Seas, and about the northern and 
southern limits of the tropical belt ; and 
decreased, by the contrary cause, in the Sea of 
Azof, Black Sea, Baltic Sea, and in the polar 
regions. The origin of the saltness of the sea is 
sufficiently accounted for when we consider that 
-the chloride of sodium and other soluble salts 
which form constituent ingredients of the globe, 
are being constantly washed out of the soil and 
rocks by rain and springs, and carried down by 
the rivers ; and as the evaporation which feeds 
the rivers carries none of the dissolved matter 
back to the land, the tendency is to accumulate 
in the sea. The principal ingredients found in 
sea-water are chloride of sodium, or common salt, 
together with salts of magnesia and lime. The 
mean quantity of salts of all kinds in the ocean is 
34-4 parts in 1000. In some parts of the Mediter- 
ranean the salinity is as high as 39-26, and of the 
Red Sea 43 ; while in the Baltic and Black Seas, 
it varies from 18 to 12. Of the mean of 34-4 
parts, about 24 are due to chloride of sodium, 4 
to chloride of magnesium, nearly as much to sul- 
phate of soda, one part to carbonate of lime, 
and -25 or one part in 4000 to silica. Up- 
wards of thirty different elementary substances 
have been already detected in sea-water, and spec- 
trum analysis may yet reveal more ; biit, except 
those named above, they exist mostly in exceed- 
ingly minute proportions, so that it is only in the 

60 



analysis of sea-weeds, marine animals, and the 
stony matters deposited in marine boilers, that 
their presence can be detected. But when we 
consider the vastness of the ocean, the absolute 
quantity of even the minutest ingredient must 
be enormous. The silver dissolved in the sea 
would far transcend * the wealth of Ind.' 

The specific gravity of the water of the ocean 
varies, of course, with the salinity ; the average 
is I '0272. Another effect of the salinity is that, 
while fresh water freezes at 32° F., the water of 
the ocean requires to be reduced to 28° ; and the 
ice then formed is porous and full of a briny fluid 
— the solid ice in fact is fresh. 

The colour and phosphorescence of the ocean 
are the next sensible properties requiring atten- 
tion. When examined in small quantities, sea- 
water is colourless ; but when viewed in the mass 
in the wide ocean, it appears to be of an azure or 
blue tint. The cause of this generally blue colour 
has not been as yet clearly explained; it would 
seem that the blue rays of light are more readily 
reflected from masses of a transparent fluid. 
While there can be no doubt that the ocean is 
generally of a blue colour, it is equally certain that 
there are many portions of sea in which a different 
hue appears. The causes of these exceptions from 
the rule seem to be of various kinds. Frequently 
the ordinary colour of the sea is affected by the 
admixture of foreign substances, these being some- 
times of a living and organic nature, and some- 
times not. Another class of cases in which 
the ocean appears to be tinged with a peculiar 
colour, is referable to the reflection of rays of light 
from the bed or bottom ; and hence, in shallow 
and clear seas, the colour of the ground is a main 
cause of any particular tint which the water may 
there assume. 

The phosphorescence of the ocean, described in 
such glowing terms by almost every voyager in 
tropical seas, is now satisfactorily ascertained to 
arise sometimes from the presence of infusorial 
animalcules, and at others from the decomposi- 
tion of vegetable and animal matter. Similar 
phenomena, arising from similar causes, exist on 
land — the glowworm, fire-fly, certain fungi, putrid 
fish, &c. — and their appearance in the one ele- 
ment need not excite greater surprise than their 
exhibition in the other. 

TIDES — CURRENTS— WAVES. 

The waters of the ocean are subject to various 
motions and fluctuations, such as tides, currents, 
whirlpools, waves. That regular ebb and flow 
known by the name of tides, and which confers 
on the ocean one of its most interesting features, 
is caused by the attraction of the sun and moon. 
By the universal law of gravitation, all masses of 
matter have a tendency to be attracted or drawn 
towards each other. The moon, therefore, as a 
mass of matter, in passing round the earth, has a 
tendency to draw the earth after it, or out of its 
natural relative position ; and it really does so to 
a small extent. As it passes round, it draws up 
the waters in a protuberance, or, in common 
language, draws a huge wave after it. But it also 
draws the whole solid globe — ^though to a less 
extent than the water immediately under it — and 
so causes the opposite side of the globe to be 
drawn away from the ocean, leaving the waters 



PHYSICAL GEOGRAPHY. 



there to form a similar protuberance or high wave. 
In the one case, the water is drawn directly up or 
towards the moon (M) ; in the other, the water is 








in some shape left" behind by the land being pulled 
away from it. In both a similar effect is produced : 
two tides {t, /) are caused at opposite extremities 
of the earth. Where the higher part of either of 
these great billows strikes our coasts, we have the 
phenomenon of high-water; and when the lower 
touches us, it is low-water. Each of the waves is 
brought over any given place in the circumference 
of the earth in twenty-four hours, so as to cause 
high-water twice a day. The sun exerts a far 
greater attractive influence on the earth than the 
moon does ; but from the great distance of that 
luminary, the difference of that attractive force on 
different parts of the globe is much less, and there- 
fore the effect in raising tides is comparatively 
small. But when this minor influence of the sun 
coincides with that of the moon, or acts in the same 
line of attraction (M/), we perceive a marked in- 
crease in the tides ; on such occasions we have what 
are called spring or large tides. When the solar 
and lunar attractions act in opposition, we have neap 
or small tides. The spring-tides happen twice a 
month, when the moon is at full and change ; and 
the neap when the moon is in the middle of its orbit 
between those two points. A tide requires six hours 
to rise— which it does by small impulses or ripplings 
of the water on the shore — and six hours to ebb or 
fall ; but every successive high-water is from twenty 
to twenty-seven minutes later than the preceding, or, 
on an average, about fifty minutes for two tides, in 
consequence of the earth requiring that time above 
the twenty-four hours to bring any given point 
again beneath the moon. The tides are thus re- 
tarded by the same reason that makes the moon 
rise fifty minutes later every day. It is evident 
that the tides will be greatest at that point of the 
earth's surface which is nearest to the moon, or 
where the latter is vertical. She is so between the 
tropics ; and accordingly the tides are there great- 
est, and they diminish as we approach either pole. 
It is further to be remarked that the moon does 
not anywhere draw up the tides immediately. In 
consequence of the law of inertia and of fluid 
friction, the tidal wave lags behind the moon. 
Moreover, in consequence of all the great seas and 
oceans forming, as we have seen, only one sheet of 
water variously distributed, the ebb and flow in 
each depend not on its own proper tide, but are the 
result of the combination of that tide with currents 
mingling with it from tides of other seas — a result 
depending upon inequalities of sea-bottom, the 
configuration of its coasts, their inclination under 
water, the size and direction of the channel which 
connects it with other seas, and occasionally upon 
winds and currents which are not tidal. So much 
do these circumstances affect the astronomical or 
primary tidal wave, that while it rises in the 
expanse of the Pacific to onfe or two feet onlyMjift. 
derived -wdcve often rises in confined or obstructed;;/ 
seas to elevations of thirty, fifty, or even a hundred 



feet ! Inland expanses of water, like the Baltic, 
Mediterranean, and Caspian Seas, and the lakes 
of North America, have no perceptible tides. 

Besides being affected by the regular motion of 
the tides, the ocean is pervaded by a system of 
currents, mostly constant, which has been com- 
pared to the circulation of the blood. These cur- 
rents play a most important part in modifying 
the climates of different regions. As respects 
the causes of oceanic currents, much remains to 
be cleared up ; but some of the leading causes 
seem well established. The t\vo prime movers 
are differences of temperature and prevalent 
winds. Sea-water does not freeze until it is 
cooled down to about 28° ; and, unlike fresh 
water, it continues to grow heavier down to that 
point. The effect of the intense cold of the polar 
regions is thus to cause a constant sinking down 
of the surface, and to establish a current of ice- 
cold water along the bottom towards the equator ; 
while, to supply the place of what sinks down, an 
in-draught or northward flow takes place on the 
surface, which brings the warm water of the 
temperate and tropical regions towards the poles. 
This is the general theory of the vertical circu- 
lation of the ocean — a circulation which might 
almost be assumed from the well-known laws of 
the flow of liquids, and which recent observations 
have established as a fact. The general prevalence 
of cold currents along the bed of the ocean from 
the poles to the equator is now beyond dispute. 
Motion once thus begun, however, is differently 
modified in each locality by the shape of the coasts, 
by prevalent winds, and other circumstances. But 
one cause which modifies all currents that tend 
either north or south, is the daily rotation of the 
earth. At the equator, any spot on the surface is 
moving eastward at the rate of looo miles an hour ; 
at 60^ north latitude, the velocity is only one half. 
Thus, the water of a current starting from the 
equator northward, is constantly coming to places 
where the bottom under it has less and less east- 
ward velocity. But, by the law of inertia, the 
water tends to retain the same velocity eastward 
with which it started, and thus it moves to the east 
of north — shooting ahead, as it were, of the bottom 
over which it is flowing, as a rider does whose 
horse slackens his pace. The contrary happens 
to a stream flowing from north to south. In this 
case, the eastward motion or motal inertia of the 
water is too slow for the parts of the bottom to 
which it successively comes ; the bottom slips in 
a manner from under it, and it falls to west of 
south. This, in combination with the action of 
opposing coasts, accounts for the circular sweep 
which many of the currents make, returning partly 
into themselves. 

Different in origin from this vertical circulation, 
though partly mixed up with it, is the horizontal 
circulation caused by prevalent winds. The best 
example of this is the Equatorial Current, which 
sets from the west coast of Africa to the east 
coast of Brazil, and which is owing to the action 
of the trade-winds. Currents caused by winds 
are always shallow, and their rate of motion 
seldom exceeds half a mile an hour : they are 
called * drift-currents,' in opposition to the deeper- 
seated 'stream-currents.' In order to feed this 
westerly equatorial current, there spring up two 
in-draught currents— the one from the north 
along t£e west coast of Portugal and Morocco, 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



the other from the Cape of Good Hope along the 
west coast of Africa as far as the Gulf of Guinea. 
When the equatorial current reaches the coast 
of Brazil, it divides into two branches. One pro- 
ceeds southwards, turning gradually eastwards 
across the Atlantic until it falls in with the 
northern in-draught from the Cape of Good Hope. 
The other branch is deflected northwards into the 
Caribbean Sea and the Gulf of Mexico. The 
water thus driven into this pent-up sea now rushes 
with accumulated momentum through the strait 
or gulf between Florida and the Bahamas, and 
forms the famous Gulf Stream. 

The Gulf Stream, after issuing from the Florida 
Strait, proceeds at first northward, parallel to the 
American coast ; but between the parallels of 35° 
and 37°, it turns gradually eastward, passing over 
the southern extremity of the Bank of Newfound- 
land, and all the while expanding in breadth and 
becoming shallower. The temperature of the 
stream, when it starts, is from 83° in summer to 
77° in winter, and even after travelling 3cxx) miles 
to the north, as high as the Banks, there is a 
difference in a winter day between its water and 
that of the surrounding ocean of 20° to 30°. Along 
its whole course a cold arctic current underlies 
it ; and this arctic current intervenes between the 
western border of the stream and the coasts of 
Florida, Georgia, and the Carolinas, the line of 
demarcation between the two being so abrupt that 
it is known as the * cold wall.' At the bow of a 
ship entering the Gulf Stream the temperature has 
been found to be 70°, while it was only 40° at the 
stem. The velocity of the stream, at its outset, is 
from 50 to 60 miles a day ; but this velocity becomes 
greatly reduced as it proceeds. 

It has usually been held that the Gulf Stream 
extends across the Atlantic to the shores of North- 
em Europe, and is the cause of the mild and 
moist climate enjoyed by the western parts of that 
continent. The opinion, however, is beginning to 
prevail that, as a distinct current, the Gulf Stream 
ceases in the middle of the North Atlantic, its 
waters being by this time thinned out to a mere 
film, and its initial velocity and distinctive heat 
having been dissipated. That warm waters from 
tropical seas are brought to the coasts of Britain, 
and even into the polar seas beyond, is proved by 
drift-wood, seeds, and fruits from the West Indies 
being frequently cast ashore on the Hebrides, the 
north of Norway, and Spitzbergen. But this is 
accounted for by the general flow of the surface- 
water towards the poles, forming part of the ver- 
tical oceanic circulation ; a flow which receives 
an eastward deflection as it proceeds northwards 
• in the way above explained. This general set 
of the surface-water is further promoted by 
the prevalence of south-westerly winds or re- 
turn-trades, which maintain a pretty constant 
north-east drift over the whole surface of the 
north-eastern portion of the Atlantic. In this 
way, although the Gulf Stream may have lost its 
original impetus, a large portion of the super- 
heated water which it brings into the centre of the 
Atlantic, must be carried to the shores of Europe 
and into the Arctic Sea. Before, however, the 
Gulf Stream loses its force as a distinct current, 
it sends off a branch southwards by the Azores 
which re-enters the equatorial current before 
described. 

While the climate of the west of Europe is thus 



ameliorated by having its shores washed by waters 
from warm seas, and by the moist and warm south- 
westerly winds that predominate, the corresponding 
coast of America is, at least, as much depressed 
by a current from the Greenland seas which flows 
southward along the shores of Labrador, carrying 
with it immense fields of polar ice, and accom- 
panied by dry and piercing winds from the north 
and north-wesL This arctic current intervenes 
between the coast of America and the Gulf Stream, 
as already mentioned, and flows under it into the 
Gulf of Mexico. 

The currents of the Pacific Ocean are little 
known ; but the Indian Ocean, exposed to a 
tropical sun and hemmed in on the north, sends 
out several large currents of warm water. One is 
the Mozambique current ; another escapes through 
the Strait of Malacca, and flows past China and 
Japan into the Pacific, making for the north-west 
coast of America. This current resembles in 
many respects the Gulf Stream. 

Two currents of equal force, but of different 
directions, meeting in a narrow passage or gut, 
will cause a whirlpool, a phenomenon which has 
ignorantly been said to be produced by subter- 
ranean rivers, gulfs, chasms, &:c., but essentially is 
only an eddy. Charybdis, in the Strait of Sicily, 
and the Maelstrom, on the coast of Norway, are 
eddies of this kind, alternately absorbing and 
casting up again whatever approaches them. 

Being an elastic and mobile fluid, water is 
readily acted upon by winds ; and thus waves are 
produced, varying in height and velocity according 
to the force and continuity of the wind, extent of 
uninterrupted surface, depth of the ocean, con- 
tending currents, and the like. The common cause 
of waves is the friction of the wind upon the 
surface of the water. Little ridges or elevations 
first appear, which, by continuance of the force, 
gradually increase until they become the rolling 
mountains seen where the winds sweep over a 
great extent of water. The velocity of waves is in 
proportion to the square root of their length. The 
large waves just spoken of proceed at the rate 
of from thirty to forty miles an hour. It is a 
vulgar belief that the water itself advances with 
the speed of the wave ; but in fact the form only 
advances, while the substance, except a little spray 
above, remains rising and falling almost in the 
same place with the regularity of a pendulum. A 
wave of water, in this respect, is imitated by the 
wave running along a stretched rope when one 
end is shaken. But when a wave reaches a 
shallow bank or beach, the water becomes really 
progressive ; for then, as it cannot sink directly 
downward, it falls over and forward, seeking the 
level Sailors and others speak of waves running 
'mountains high ;' but, according to Scoresby, 43 
feet is about the utmost difference of level between 
crest and trough in ocean-waves. 



LAKES AND RIVERS. 



Lakes are inland bodies of water not connected 
with the ocean or any of its branches : they are 
generally fresh, but are occasionally brackish, or 
even decidedly salt They are classified according 
as they are fresh or saline, and according to the 
manner in which they receive and discharge their 
waters — namely, those that both receive and dis- 
charge running water ; those that receive waters. 



1 

re 1 



PHYSICAL GEOGRAPHY. 



but have no visible outlet, as the Caspian Sea; 
those which receive no running water (being fed 
by springs), but have an outlet ; and such as 
neither receive nor discharge running water. Lakes 
are distributed over the globe according to the 
inequalities of surface ; and all tend to annihila- 
tion, partly by silting up their basins, and partly by 
•deepening their outlets, thereby effecting an entire 
drainage of their waters. The most gigantic are 
those of North America — such as Superior, Huron, 
Michigan, Erie, and Ontario, which respectively 
occupy 32,000, 20,000, 16,000, 10,000, and 7200 
square miles. Next in order are the lakes of 
Africa, three of which — Victoria Nyanza, Albert 
Nyanza, and Tanganyika — are estimated at 29,900, 
25,400, and 10,400 respectively. The largest lakes 
in Asia are Aral and Baikal ; the surface of the 
former is estimated at 23,000, and the latter at 
15,000 square miles. Europe can boast of a vast 
number, which, though generally small, give 
beauty and diversity to her landscapes. Those 
of Ladoga and Onega, in Russia, are the largest ; 
the former having a surface of 6330, and the latter 
of 3280 square miles. A comparative estimate of 
the extent of these vast sheets may be formed when 
we mention that the area of Lake Geneva does 
not exceed 340 square miles. 

Lakes subserve important purposes in the 
economy of nature. They serve as reservoirs for 
the waters which rivers would too speedily carry 
away from the land ; they are the tanks, as it 
were, in which the impurities of streams subside ; 
they refresh and enliven the landscape ; and as 
they all tend to silt up their own sites, these sites 
become in time tracts of fertile alluvium, and such 
has been the origin of some of our finest plains. 

Rivers, streams, springs — whether flowing with 
a volume several miles in breadth, or trickling in 
a tiny rill which a child's hand might obstruct — 
constitute a class of the most valuable agencies in 
the physical history of our globe. They are the 
irrigators of its surface, adding alike to the beauty 
of the landscape and the fertility of the soil ; they 
carry off impurities and every sort of waste debris, 
to be deposited in the ocean as the strata of future 
continents ; and when of sufficient volume, they 
form the most available of all channels of commu- 
nication with the interior of continents. Rivers 
originate in the rain and snow which descend from 
the sky (see Meteorology). Falling on the 
surface, the water percolates the soil, finds its 
way through the rents, fissures, and pores of the 
rocky strata, and ultimately escapes at some lower 
level in the form of springs. Some of these 
springs are perennial, others temporary or inter- 
mittent : some are limpid, and almost absolutely 
pure ; others are impregnated with metallic, earthy, 
and saline ingredients, according to the nature of 
the strata through which they have percolated : 
some are cold, others tepid; while many issue, 
with bubbling and steam, near the ordinary boil- 
ing-point of water. Springs, naturally tending to 
lower levels, unite and form streams; and thfese, 
again, falling still lower, conjoin in valleys, and 
form rivers — creating in their course rapids, 
cataracts, and waterfalls, ravines and dells, lakes, 
swamps, and marshes, alluvial plains, and low 
terminating deltas. The valley in which a river 
flows is usually termed its basin; and its drainage 
is that portion of country drained by its streams 
or tributaries ; the terms are often used syn- 



onymously. To compare merely the lengths of 
rivers is far from conveying a correct idea either 
of their physical or economical importance ; the 
extent of their basins is an equally important item. 
The following is a comparative view of the length 
and drainage of some of the principal rivers on 
the globe, headed by the Thames as a standard 
of comparison. 



Principal Rivers. 



Europe — 

Thames 

Vistula 

Loire 

Rhine 

Elbe 

Don 

Dnieper 

Danube I 1750 

Volga I 2320 



Length 

in 
Miles. 



250 

800 
600 
900 



Asia — 

Euphrates 

Indus 

Ganges 

Yang-tze-kiang. 

Amoor 

Obi 



Africa — 
NUe. 



America — 

St Lawrence 

Mississippi — Missouri. 

La Plata 

Amazon 



1800 
1800 
1500 
3600 
2700 
2000 



Sooo(?) 



2000 

4400 
2000 
4000 



Drainage 

in 

Square Mile*. 



600 

7S.OOO 

45.250 

86,000 

58,800 

224,000 

226,000 

250,000 

500,000 



260,000 
250,000 
300,000 
700,000 
780,000 
1,350,000 



(?) 



297,000 
1,244,000 
1,250,000 
2,000,000 



CLIMATOLOGY. 

The climatology of the globe relates to the degree 
of heat and cold to which its respective countries 
are subject, the dryness and moisture of the air, 
and its salubrity or insalubrity as influenced by 
these and other causes. As yet the minutiae of 
climate are but imperfectly determined ; the fol- 
lowing general causes, however, have been suffi- 
ciently ascertained : i. The action of the sun upon 
the soil and atmosphere ; 2. The internal heat of 
the globe ; 3. The height of the place above the 
sea ; 4. The general exposure of the region ; 5. The 
direction of its mountains relatively to the cardinal 
points ; 6. The neighbourhood of the sea, and its 
relative position ; 7. The geological character of 
the soil; 8. The degree of cultivation which 
it has received; and 9. The prevalent winds. 
These causes, acting together or separately, deter- 
mine the character of a climate as moist and 
warm, moist and cold, dry and warm, dry and 
cold, &c. ; and this climatic character is the main 
influence which determines the nature and amount 
of vegetable and animal development The several 
subjects belonging to this section are treated in 
detail in the number on METEOROLOGY. 

DISTRIBUTION OF PLANTS AND ANIMALS. 

The life of the globe— that is, its vegetable and 
animal productions — constitutes its most import- 
ant and exalted feature as a creation. All the 

63 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



varied materials of which it is composed, all the 
complicated actions, reactions, and mutations to 
which they are subject, are humble phenomena 
compared with the production of the lowliest or- 
ganism. This life is everywhere : the waters teem 
with it, the dry land from pole to pole is clad with 
it ; nay, there is life within life, and perhaps there 
exists not a single plant or animal but becomes 
in turn an abode for others of more diminutive 
dimensions. Speculations as to the origin and 
generic classification of vegetable and animal 
life belong not to our subject. Geography views 
them simply as they exist, and endeavours to 
determine the laws which regulate their distri- 
bution. 

Vegetables are regulated in their terrestrial dis- 
tribution by conditions of soil, heat, moisture, light, 
height of situation, and various other causes ; in 
the waters, by depth, heat, light, nature of bottom, 
and the presence of mineral and saline ingredients. 
Were it not for these causes, there is no reason 
why the tribes and genera of one region should 
not be identical with those of another — why the 
palms of India should not flourish alongside the 
oaks of England, the oaks of England with the 
pines of Norway, or these again with the dwarf 
birches of the arctic regions. As it is, the tropics 
have genera unknown to the temperate zone, 
and every advance poleward brings us in contact 
with new and peculiar species. Temperature in 
this case seems to be the grand regulating con- 
dition ; and as this is effected by elevation, as well 
as by increase of latitude, we find the mountain- 
ranges near the equator presenting all the features 
of a tropical, temperate, and even arctic vegeta- 
tion. Thus palms and plantains may luxuriate at 
their bases ; then appear oranges and limes ; next 
succeed fields of maize and wheat ; and still higher, 
commences the series of plants peculiar to tem- 
perate regions. In temperate latitudes, though the 
variety of vegetation be less, similar phenomena 
present themselves. Besides these great climatic 
effects, there are others depending on soil, mois- 
ture, light, &c., which, though limited, are not less 
imperative. Thus, the southern slope of a hill is 
generally clothed with species distinct from those 
on the north ; a limestone district presents a carpet 
of vegetation widely different from that of the 
clayey moorland : some tribes flourish in the moist 
valley, which would die on the open plain; some 
tribes thrive in the marsh, others on the dry upland ; 
some luxuriate under the influence of the sea-spray, 
which would be instant destruction to others. But 
whilst most species are subject to these laws, there 
exists in the constitution of many a certain degree 
of elasticity which admits of their adaptation to a 
wider range — a beneficent arrangement, which 
permits man to extend through cultivation those 
grains and fruits upon which his subsistence so 
essentially depends. (For further and more minute 
information respecting the laws which regulate the 
dispersion and distribution of plants, see Vege- 
table Physiology.) 

The animals which people the globe are sub- 

64 



jected to somewhat similar laws of distribution. 
Some are strictly tropical, others confined to the 
temperate zone ; while not a few are destined to 
find their subsistence wholly within the polar 
circles. Besides this general distribution, we find 
a more particular restriction to certain continents- 
and tracts where peculiarities of soil, climate, and 
food seem to be the governing conditions. Thus^ 
the elephant roams only in India, Burmah, and 
Africa ; the ostrich in Africa ; the rhea in the 
pampas of South America ; the kangaroo in Aus- 
tralia ; the reindeer within the arctic circle ;. 
the polar bear amid the snows of Greenland and 
Labrador ; and so on, as will be more minutely 
shewn under Zoology. Similar laws are im- 
pressed on the life of the ocean. The ' right * 
whale, as it is termed, of the northern hemisphere, 
is a different animal from that of the southern ; for 
' the tropical regions of the ocean are to him as a 
sea of fire, through which he cannot pass, and into 
which he never enters;' while the sperm whale 
delights in warm water. The herring finds its 
chosen habitat in the Northern Sea ; the oyster 
clings to a peculiar bottom, at a certain depth ; 
the cod inhabits the same banks and shoals for 
ages ; and a few fathoms of greater or less depth 
would be more fatal to many species of shell-fish 
than the dredge of the fisherman. As on plants, 
so on animals, altitude exerts a very decided influ- 
ence ; and we do not exaggerate when we affirm 
that a lofty mountain-range presents a more im- 
passable barrier to vital distribution than the 
widest expanse of ocean. Though presenting a 
close analogy in the manner of their distribution, 
plants and animals differ in this respect, that 
many tribes of the latter — birds, fishes, and mam- 
malia — make periodical migrations of vast extent ; 
food and proper breeding-places being the objects 
of their search. These migrations must not be 
confounded with that adaptability of constitution 
which fits the horse, the dog, the ox, the sheep^ 
the pig, and other domestic animals, to be the 
companions and supports of man in his onward 
possession of the globe. The one is but a change 
of place in search of food, under a congenial tem- 
perature ; the other amounts to a constitutional 
change, irrespective of climatic influence. 

Man, of all animals, has the widest geographical 
distribution. This he enjoys not only from the 
greater adaptability of his constitution, but from 
that superior intelligence which enables him to- 
counteract the effects of climate by clothing, 
houses, fire, and the storing of provisions. It may 
be justly affirmed, therefore, that there is no region 
where man may not exist and carry on the pur- 
poses of life in a higher or lower degree of civil- 
isation. Though generally regarded as a single 
species of a single genus, naturalists have divided 
mankind into several varieties, according to their 
more prominent physical features; and ethnolo- 
gists, extending the subject according to minor 
features, language, and so forth, have subdivided 
these varieties into branches, tribes, and families^ 
See Ethnology. 



VEGETABLE PHYSIOLOGY. 



THE science which embraces the study and 
investigation of the vegetable kingdom, is 
known by the name of Botany, from the Greek 
word botani, meaning an herb or grass. That 
department of the subject which explains the or- 
ganisation and vital functions of plants, is called 
Vegetable Physiology ; and that which recognises 
their arrangement into orders, tribes, genera, and 
species, according to their respective forms and 
qualities. Systematic Botany. The one relates to 
functions which are common to all vegetables, the 
other takes notice only of those structural pecu- 
liarities which serve to distinguish one species 
from another, and to enable the botanist to form 
these into natural and artificial groups. It is to 
the former of these departments that we now direct 
attention. 

GENERAL ECONOMY OF VEGETATION. 

Nature arid Functions of Plants. — The sim- 
plest forms of life are observable in certain 
plants and animals, whose economy is limited to 
the absorption and assimilation of nutriment, and 
the power of reproduction ; and the difference 
between these inferior forms is so trifling, that in 
them the animal and vegetable kingdoms seem to 
pass into each other. The absolute differences 
between plants and animals are indeed difficult 
to define, when they are to be applied to all plants 
and to all animals. In many cases, form and 
structure afford no decisive characters whereby we 
may separate the two kingdoms from each other ; 
while phenomena usually regarded as pertaining 
to the animal kingdom are prevalent in the lower 
forms of plants, and indicate that no reliance can 
be placed upon their mode of life. In like manner, 
the chemical distinctions upon which much de- 
pendence has hitherto been placed, give way before 
increased knowledge ; for cellulose and starch, 
long considered as peculiarly vegetable products, 
are now known to occur in animal structures. 
The locomotive power of many of the lower algae 
is greater than that of many animal organisms ; 
and even the spores, or seeds, of some algae of more 
complex organisation, move about when freed 
from their parent, with an activity which appears 
truly animal, by means of the cilia with which they 
are provided. When the spore finds a suitable 
resting-place, its movements cease ; and having 
thus exchanged its animal-like mode of life for one 
of a less erratic character, it becomes developed 
into a beautiful alga in all respects resembling its 
parent. The two classes, plants and animals, 
seem, as it were, to start from a common point at 
the base, the inferior forms bearing a certain simi- 
larity in structure and functions, which gradually 
disappears as we ascend in the scale of develop- 
ment. 

Plants derive their food partly from the soil and 
partly from the air ; and whatever they take must 
either be reduced to a liquid or to a gaseous state. 
The ultimate elements of which plants are com- 
posed are — carbon, oxygen, hydrogen, and nitro- 
gen. Of these, carbon, which is a solid substance, 
5 



is the principal ; and as it is insoluble in water, it 
must be combined with oxygen, so as to form 
carbonic acid gas, before it can be taken up \vf 
plants. Oxygen is the next in abundance, and it 
IS absorbed principally when combined with nitro- 
gen, in the form of atmospheric air. Hydrogen b 
not found in a free state in the atmosphere, and 
therefore it can only be taken up by plants whea 
combined with oxygen, in the form of water, or 
with nitrogen, as ammonia, in which last form it 
exists in animal manure. Nitrogen, though found 
in very small quantities in plants, is an important 
element, as it constitutes the principal ingredient 
in the gluten, which is the most nutritive part of 
corn and other seeds, and which is essential to the 
germination and nourishment of young seedling 
plants. Nitrogen also appears to be a principal 
agent in the production of colour in leaves and 
flowers, especially when they first expand. As 
oxygen is imbibed by plants in combination with 
all the other elements of which they are composed, 
it is not surprising that the plant takes up more 
of this gas than it requires ; and, consequently, it 
has been furnished with a remarkable apparatus 
in the leaves, to enable it to decompose the car- 
bonic acid and other gases which it has absorbed, 
and to part with the superfluous oxygen. Plants 
are thus found to improve the air by the removal 
of carbonic acid, which is injurious to animal 
life, and by the restoration of oxygen, which is 
favourable to it ; and so to maintain a neces- 
sar)' equilibrium in the atmosphere, as animals 
are continually absorbing oxygen, and giving out 
carbonic acid. Light being essential to the 
decomposition of carbonic acid gas in the leaves, 
oxygen is not exhaled by plants during the night; 
but, on the contrary, a small quantity of car- 
bonic acid gas escapes, and oxygen is absorbed. 
These processes have been called the respiration 
of filaritsj but they are very different from the 
respiration of animals. 

Development of Vegetable Life. — This depends 
upon the concurrence of certain agents, the prin- 
cipal of which are — heat, air, moisture, light, and 
soil. No seed can germinate without the concur- 
rence of the three agents of heat, air, and moisture ; 
but in the growth of most plants, the agency of 
soil and light is also necessary. Every perfect 
seed contains the germ or embryo of a new plant 
of the same kind as the parent, and a portion of 
concentrated carbon and nitrogen, in the form of 
starch and gluten, laid up to serve as nutriment 
for the young plant, till its organs are sufficiently 
developed to enable it to seek food for itself. This 
nutrient matter is either cont?ined in the tissues of 
the embryo's cotyledons, or laid up beside it in the 
seed, in the form of separate albumen. The seed 
is generally furnished with a hardened covering, 
in order to preserve it in an inert state as long as 
may be necessarj'. The common bean will afford 
a familiar example of the process of germination. 
As soon as it is put into the ground, it is acted upon 
by the influence of heat and moisture, which dis- 
tend its tissues, so as to burst the external integu- 
ment The agency of the air is next required to 

65 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




combine with the store of nutriment laid up in the 
seed, and to fit it for the purposes of vegetation. 
The first organ which ex- 
pands in the embryo of a 
young plant is the radicle, 
or root c. There is a small 
opening (foramen) in the 
covering of the seed, to- 
wards which the point of 
the root is always turned, 
in order that it may be 
protruded without injuring 
its soft and delicate tex- 
ture. The radicle takes 
up water and air, and 
transmits the Hquid thus 
formed to the other tis- 
sues. The nutritive sub- 
stances laid up in the 
cotyledons, or seed-lobes {a a), become quite 
changed during the process of germination. The 
starch, which is insoluble in water, is rendered 
soluble by the action of a peculiar substance called 
diastase, derived from the gluten, which acts as a 
ferment. This substance has so powerful an effect 
upon the starch as to render it instantly soluble, 
and thus nutriment is prepared for the use of the 
infant plant. The starch is changed into sugar ; 
and when the store of starch and gluten has been 
exhausted, the plant is able to subsist by its own 
assimilating powers, at the expense of the air and 
the soil 

Heat, though essential to germination, is injuri- 
ous, unless it be combined with moisture. A high 
degree of dry heat will parch seeds, and destroy 
their vitality ; hence, when they are to be kept for 
food, it is not unusual to dry them in an oven, to 
prevent them from germinating. When combined 
with moisture, a very high temperature is not inju- 
rious to many kinds of plants, especially those of 
low organisation ; for example, various species of 
plants inhabit the hot springs of Italy and the hot- 
water pools around the geysers in Iceland ; while, 
on the other hand, certain lichens and mosses grow 
in the region of perpetual snow, where the tem- 
perature seldom rises to 32° Fahrenheit. Warmth 
is not only necessary for the germination of the 
seed, but also for the growth and after-development 
of the plant. In flowering plants the sap will not 
rise without a certain degree of heat. Cold will 
also check the development of the flowers and 
fruit, and even of the leaves, and will prevent the 
full flavour being attained by the fruit. The secre- 
tions of plants are diminished by cold. 

Moisture must be combined with heat and air to 
render it useful to vegetation. An excess of mois- 
ture without heat, and combined with air, induces 
decay in seeds, instead of exciting them to germi- 
nate ; and an excess of moisture is injurious even 
to growing plants, as it destroys the delicate tissue 
of the root spongioles. 

Air is essential both to the germination of the 
seed and the development of the plant. Without 
oxygen from the atmosphere, the carbon laid up in 
the seed cannot be made available for the use of 
the infant plant, as carbon in its concentrated state 
is insoluble in water, and requires to be combined 
with oxygen to convert it into carbonic acid gas. 
In like manner, air is essential through all the pro- 
cesses of vegetation ; no wood can be formed, no 
seed ripened, and no secretions produced, without 



abundance of carbon ; and this cannot enter the 
plant, even from the soil, without a constant supply 
of oxygen from the air. 

Light is not required for the germination of 
seeds, but it is essential to the development of 
plants, as it occasions the decomposition of the 
carbonic acid contained in the parts exposed to its 
influence ; without which the plant could not assim- 
ilate the carbon. Colour also appears to depend 
partly on light. Plants grown in darkness are of 
a sickly aspect, and are said to be etiolated, or 
blanched. 

In addition to the elements of which plants are 
principally composed, there is also found in their 
substance a quantity of inorganic matter, which 
differs according to the nature of the plant, and 
which appears to be derived solely from the soil. 
Plants require different kinds of inorganic food, 
according to their nature, and appear to possess 
the power of selection, as they only take the kind 
they need, though it may form but a very small 
portion of the soil in which they grow. Thus it 
is evident that any particular crop must in time 
exhaust the soil in which it grows of the requisite 
inorganic matters, unless they should be renewed 
by the addition of what are called mineral manures 
(see Agriculture); and it is also clear that 
crops requiring another kind of earth may succeed 
in the same soil after it has become unproductive 
for the first kind of crop. Hence the neces- 
sity for what is called the rotation of crops — 
that is, for letting crops of a different nature 
succeed each other in fields and gardens. Wheat, 
barley, rye, and oats are silica plants ; pease, beans, 
and clover, lime plants ; and turnips and potatoes, 
potash plants. Thus, these crops, from the differ- 
ence in their predominant inorganic ingredients, 
are generally made to alternate with each other. 
In some soils containing a large amount of phos- 
phates and other organic matters, the same plants 
may be cultivated successfully for a number of 
years. 

Term of Vegetable Existence. — ^The longevity of 
plants differs according to their nature and the 
circumstances in which they are placed : thus, 
plants are annuals, which grow only one season, 
and die as soon as they have ripened their seed — 
biennials, which generally last for two years— or 
perennials, which last for several years. Trees 
and shrubs, which have ligneous or woody stems, 
are destined to remain undecayed for years. The 
term shrub is applied to those woody plants which 
branch out from near the root, and seldom attain 
a great height ; while trees have, generally speak- 
ing, only one stem or trunk proceeding from the 
root to a considerable height before it divides into 
branches. The length of time which trees live 
depends in a great measure on the situations in 
which they grow. The age of trees was formerly 
calculated by their diameter, or by the number 
of concentric circles or layers in the trunk ; 
but both these modes are now found to be often 
fallacious. According to the first, it was sup- 
posed that if a tree attained the diameter of a 
foot in fifty years, fifty years should be counted 
for every foot it measured in diameter ; and thus 
it was supposed that the great baobab tree, found 
by Adanson on the banks of the Senegal, which 
measured nearly thirty feet in diameter, must 
have been about 6000 years old, or coeval with 
the world itself. It is found, however, that the 



VEGETABLE PHYSIOLOGY. 




baobab, like all soft-wooded trees, grows rapidly, 
and attains an enormous diameter in less than a 
hundred years. The mode of counting by con- 
centric circles only applies to exogenous trees, and 
even with them is very uncertain. A warm spring, 
which sets the sap early in motion, followed by 
weather cold enough to check vegetation, will give 
the appearance of two layers in one year, as the 
recommencement of vegetation will have the same 
appearance as a new layer in spring. In many 
trees, such as the oak, for example, a second 
growth often takes place after midsummer ; so 
that even a third layer is occasionally formed in 
the course of six months. On the other hand, it 
is possible that a moist warm winter, by keeping 
an evergreen tree growing the whole year without 
any check to vegeta- 
tion, might give the 
appearance of only one 
layer to the growth of 
two years. Notwith- 
standing these anom- 
alies, practical men find 
counting the concentric 
circles of a tree the 
best mode which has 
yet been discovered of 
ascertaining its age, as 
in northern countries only one growth is made 
in the course of a year. The accompanying figure 
represents a section of an exogenous or outside- 
growing stem five years old, having the pith in 
the centre, a cylindrical layer for every year of the 
growth, the bark on the outside, and the medullary 
rays passing from the centre to the circumference. 

DISTRIBUTION OF PLANTS. 

The geographical arrangement of the vegetable 
world is influenced by conditions of soil, heat, 
moisture, light, altitude of situation, and various 
other causes ; for, did they flourish independentiy 
of these conditions, then there were no reason why 
the vegetation of one part of the globe should differ 
from that of another. The flowers, shrubs, and trees 
which adorn the plains of India, are not the same 
as those which clothe the valleys of Britain ; and 
these, again, are totally different from the scanty 
vegetation of Iceland or Spitzbergen. Each species 
is, nevertheless, perfectly adapted to the conditions 
under which it exists, and finds in its native situa- 
tion all the elements required for its growth. 

In a state of domestication, however, many 
species exist in regions far beyond the limits of 
their original distribution. Our cultivated useful 
plants are of this kind ; as, for example, the potato, 
which is a native of tropical America, and is of 
the highest utihty in Northern Europe. In South 
America, the warm climate enables it to propagate 
by the seed ; hence in that region its tubers are 
small and insignificant ; but in Europe, where the 
climate is unfavourable to the production of the 
plant from seed, it propagates by the tubers, which 
are consequently enlarged, so as to contain a store 
of nutriment for the young plant, before its stem 
and leaves be sufficiently developed. 

The habitats of plants — that is, the situations in 
which they naturally thrive best — are generally 
distinguished as follows : Marine, when the plants 
float upon, or are immersed in, salt water, such 
as sea-weeds ; and maritime, when they grow by 



the sea-shore, or m places exposed to the influence 
of the sea-breeze. Aquatic is the general term 
for fresh-water habitats ; and these may be lacus- 
trine, that is, growing in lakes— fluviatiU, in 
rivers — or palustrine, when in marshes or wet 
meadow-lands. Plants are also distinguished as 
growing in open pastures, in cultivated lands, 
woods, mountainous parts, and in caves, mines, 
and other underground excavations. The term 
epiphyte indicates that the species grows upon 
others without deriving from them the elements 
of nutrition ; and parasite, that it adheres to their 
surface, enters their tissue, and directly extracts 
its nourishment. Examples of epiphytes are seen 
in numerous species of tropical orchids, and para- 
sites in such plants as the mistleto, dodder, and 
Broom-rapes. The range of habitat is that extent 
of the earth's surface over which a plant is dis- 
tributed by nature. The terms maritime and 
alpine, for example, are general in their applica- 
tion, and refer to all plants which grow by the 
sea-side or on mountains ; but the plants which 
flourish on the sea-shores of Great Britain are not 
the same with those on the coast of Africa ; nor 
are these, again, identical with the maritime vege- 
tation of Chili. The geographical range of any 
plant conveys a more special idea, and embraces 
only that particular tract over which the species 
extends. This range is circumscribed by con- 
ditions of temperature, light, and elevation above 
the sea, and does not, as might be supposed, 
depend very closely upon belts of longitude, by 
which temperature is generally indicated. Thus, 
nearly all the beautiful Pelargoniums and Mesem- 
bryanthemums which adorn our green-houses are 
natives of a limited space near the Cape of Good 
Hope, as are also many of our most beautiful 
bulbs. The curious Stapelias, that smell so much 
like carrion, are found wild only in South Africa. 
The different kinds of Eucalyptus and Epacris 
are restricted to Australia. The Umbelliferous 
and Cruciferous plants spread across Europe and 
Asia ; the Cacti are found in tropical America ; 
and the Labiatae and Caryophyllaceae are seldom 
found beyond Europe. The peculiar ranges and 
centres of vegetation, as they are termed, cannot 
be sufficiently understood, however, without a 
knowledge of the different tribes and classes of 
plants, the consideration of which forms the sub- 
ject of next paper— Systematic Botany. 

Soil exercises less influence on the distribution 
of plants than is usually ascribed to it, though 
there can be no doubt that on its power of absorb- 
ing and retaining heat and moisture much of the 
luxurious growth of vegetables depends. They 
will grow to some degree in almost any soil, as the 
bulkier ingredients — clay, lime, and sand — always 
predominate ; but a proper proportion of these 
earths is necessary to perfect vegetation, and many 
plants will not continue healthy and propagate 
unless supplied with other elements, such as potash, 
soda, and various metallic salts. For this reason, 
the natural vegetation of a limestone country differs 
from that of a retentive clay ; while the plants 
which cover sandy downs are different from those 
of the alluvial valley. Moisture, which is indis- 
pensable to the existence of vegetation, also exer- 
cises great influence in its natural distribution. 
Very dry regions are deficient in vegetable forms, 
while their luxuriance in tropical countries is con- 
nected with great heat and moisture. The plant 



CHAMBERS'S INFORMATION FOR THE PEOPLE, 



which roots in the parched sand is furnished with 
leaf-organs to absorb moisture from the atmos- 
phere, and retain it ; while in a wet situation these 
organs would become diseased, and rot away ; so, 
in like manner, a marsh-plant, whose spongioles 
are its main organs of sustenance, would perish 
were it removed to an arid soil. The organic 
structure of such plants forms a limit to their 
distribution ; and the same may be said of the 
Salicornia, Salsola, Lepigomcm marinum, &c., 
which live only when exposed to the salt spray of 
the ocean. 

Heat and light are perhaps the most manifest 
agents in the distribution of vegetable life. The 
luxurious growth of the tropical jungle is the 
direct result of warmth and moisture, just as the 
barrenness of Nova Zembla is the effect of piercing 
cold ; yet both situations are inhabited by plants 
which enjoy the conditions peculiar to their exist- 
ence. No conditions of mere soil, or light, or 
moisture, could make the palms, tree-ferns, and 
jungle-flowers of India flourish in Great Britain ; 
so neither would our oaks or pines flourish in 
Iceland, unless we could provide for them that 
temperature and seasonal influence necessarj' to 
their healthy existence. Light, though it acts 
most powerfully on the colours and blossoms of 
plants, is in some measure an element in their 
geographical arrangement. The northern side of 
a hill may sometimes be as gi'een, but it never 
will be so flowery as the southern. The more free 
the exposure, the more readily will most plants 
also blossom, and yield a rich fruit. So well is 
this understood in the grape-countries on the 
Rhine, that the right bank of that river, which 
faces the sun, is reckoned to be much more 
valuable than the left, and commands a higher 
price for its wines. 

Altitude, or elevation above the ordinary sea- 
level, also exerts an obvious influence on the dis- 
tribution of vegetable life : it is equivalent to 
removal from a tropical to a temperate region, 
or from temperate latitudes to the arctic circle. 
For every hundred feet of ascent, there is a pro- 
portional fall of the thermometer ; so that, at the 
height of 5000 feet in the latitude of Britain, and 
16,000 at the equator, we arrive at the region of 
perpetual snow. This intimate relation between 
altitude and decrease of temperature accounts for 
the fact, why the base of a mountain may be 
clothed with the vegetation of tropical India, the 
sides with that of temperate England, and the 
summit with the mosses and lichens of icy Lab- 
rador. 'We may begin the ascent of the Alps, 
for instance, in the midst of warm vineyards, and 
pass through a succession of oaks, sweet chestnuts, 
and beeches, till we gain the elevation of the more 
hardy pines and stunted birches, and tread on 
pastures fringed by borders of perpetual snow. 
At the elevation of 1950 feet, the vine disappears ; 
and at 1000 feet higher, the sweet chestnuts cease 
to thrive ; 1000 feet farther, and the oak is unable 
to maintain itself; the birch ceases to grow at an 
elevation of 4680 ; and the spruce-fir at the height 
of 5900 feet, beyond which no tree appears. The 
Rhododendron ferrugineum then covers immense 
tracts to the height of 7800 feet ; and the herba- 
ceous willow creeps 200 or 300 feet higher, 
accompanied by a few saxifrages, gentians, and 
glasses ; while mosses and lichens struggle up 
to the imperishable barrier of eternal snow.' 

68 



The circumstances which facilitate the dis- 
persion or migration of plants, are not uncon- 
nected with the causes which limit their geo- 
graphical distribution. Many seeds drop from 
the parent stalk, spring up into new series of 
stems, which in turn give birth to another race 
of seeds, and these again to another circle of 
vegetation. Thus, any species of plant would 
spread from a common centre till arrested by the 
influences which limit its range of habitat ; and 
this mode of dispersion no doubt frequently 
occurs. In most plants, however, the seeds are 
small and light, and easily borne about by the 
winds : some are downy, and furnished with wings 
or hairs, while others are ejected from their car- 
pels with considerable force. All these appendages 
and peculiarities are evidently intended to facilitate 
their dispersion, which is further assisted by rivers^ 
lakes, and tidal currents, by the wool of animals^ 
the droppings of birds, and the economical pur- 
suits of man, whether accidental or intentional. 

STRUCTURE OF PLANTS, 

In order to explain the varied phenomena of 
plant-life, we must revert to the elementaiy tissues 
of which the various organs are composed. It 
is in these tissues that the processes of growth 
and multiplication, of individual development and 
of reproduction, can alone be accurately traced. 
Vegetable Histology limits itself to such investiga- 
tions. If we cut a thin slice from the leaf or 
succulent stem of a plant, and place it under the 
object-glass of a microscope, we shall find it to 
present the general appearance of a web or tissue^ 
more or less of a honeycomb form, 
as represented in the wood-cut {a). ^^o^^L. 
If more carefully examined, it will ^^^P^^^ 
be found that the apparent meshes )0O9^^^ 
of the network are not hollow 2(§^^^0'y 
spaces in a homogeneous mass or T^OOQQ^ 
membrane, but that each has its QOO^Or 
own envelope — is, in fact, a minute ^OOC^O^ 
bladder or vesicle, or elongated "^(^MCJC 
tube, as the case may be ; and that "V "ii^^f 

the whole mass of tissue is formed n n 1 ..• 

, ., ^- c u • <^> t'ellular tissue, 

by the aggregation of such vesi- ' 

cular or tubular bodies held together by means 
of an imperceptible layer of intercellular matter, 
which causes the contiguous cell-membranes to 
cohere. In the tissues of plants there is an infinite 
variety, both as regards the form and an-angement 
of their elementary bodies, but all may be reduced 
to three distinct types of structure, to one or other 
of which every modification can be referred. These 
are distinguished as the cellular, woody, and 
vascular tissues. 

Cellular tissue {Parenchytna) may be said, in 
general terms, to form the soft and succulent parts 
of plants — as, for example, the pith of trees, the 
delicate central tissue of Papyrus, shewn in the 
following figure {b), and the soft parts of our 
esculent vegetables and fruits. It is composed of 
minute bladders or vesicles, which are called cellsy 
which have their walls composed of a chemical 
substance called cellulose. Cells are seldom so 
large as to be visible to the naked eye, but are 
readily seen under a compound microscope. They 
usually consist of a pellucid membrane, and con- 
tain a formative protoplasm in their interior, with 
nuclei and nucleoli, which give origin to new cells. 



VEGETABLE PHYSIOLOGY. 



Starch, gum, sugar, oil, resin, colouring matter, 
air, crystals, and other nitrogenous substances, are 




t, Papyrus : pith-like tissue, composed of cells arranged 
in form of a network, so as to leave large intercelli3ar 
spaces (ad nat.). 

also found in the cells of plants. Starch is a very 
abundant substance in cells, serving purposes of 
nutrition, and may be readily seen by placing 
under the microscope a thin slice of potato upon 
which a drop of tincture of iodine has fallen ; this 
induces a beautiful blue colour in the starch- 
granule, and is a constant test for the occurrence 
of starch. Starch usually occurs in the form of 
minute grains, many of which are contained in 
each cell. Their form is often constant and char- 
acteristic in certain plants — for example, the very 
minute angular starch-granules of rice are quite 
different from those of the other cereal grains, 
which, again, are easily distinguished from those 




c. Starch-grains of Potato {ad nat.). 

of the potato, shewn in the above figure {c) ; while 
those of leguminous plants have a somewhat 
common character {d). The peculiarities of 
starch-granules have been successfully employed 
in detecting adulterations of food and drugs, and 
for other purposes of practical utility. 

The cell in many cases displays a thickened 
opaque wall and an empty cavity within. This 
arises from the deposit of woody matter on the 
interior surface of the cell-wall, which is seen in 
the hard stone of the cherry and in the shell of the 
coco-nut, both of which consist of cellular tissue 
equally with the softest parts of their respective 
fruits, and owe their solidity to the indurated 
woody matter. Instead of having the whole inner 



surface of the cell covered in this way, the de- 
posited matter may be so arranged as to cover 




d. Lentil : cells of seed containing Starch-grains 
{fld nat). 

certain parts only : it is often deposited in the 
form of rings or spiral coils ; and in the latter case 
gives rise to the beautiful spiral cells seen in the 




e. Spiral tissue firom the root of an Epiphytal Orchid 
(ad nat.). 

leaves and roots of epiphytal orchids {ey, and in 
the leaves of bog-mosses (Sphagna). 

With respect to their general form, cells are 
exceedingly variable, and are usually greatly modi- 
fied according to the position in the plant which 
they occupy. They very commonly present the 
hexagonal appearance represented in the wood- 
cut {a) ; but in the bark and young stems, as well 
as in roots and other parts, they often assume an 
oblong form (fig. e) ; sometimes resembling the 
bricks of a wall set on end, and thus indicating 
the manner in which plant-structure is built up, as 
it were, by separate cells cemented together. 

The rounded or spherical form may be regarded 
as the normal form of the cell, the two modifica- 
tions to which we have alluded arising from the 
pressure of spherical or oval cells in contiguity, or 
special modifications intended to fit them for their 
place in the structure. In many cases, however, 
we find cells of a very different form, whose modi- 
fications obviously arise from certain special func- 
tions which they are designed to perform- The 
pith-like substance of the rush, used as wick for 
'rush-lights,' consists of cells of a most beautiful 
stellate form; the free cells or spores of certain 

63 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



algae are covered with cilia, which give them loco- 
motive power ; the cells of hairs are elongated, 
and often much branched ; and the cells of unicel- 
lular algae, such as the Desmideae and Diatomacea?, 
often display the most exquisite symmetry, both 
in outline and in the elaborate sculpture of their 
surface. The cotton hair, which is a cell in 
peculiar condition, presents the form of a flat 
twisted band with a thickened margin, a character 
which is retained by it after it is dressed, spun, 
and woven into cloth, and even after that cloth 
has been worn to rags, reduced to pulp, and 
remanufactured into paper. 

In the pulp of leaves and fruit, and in the 
cellular tissue of the bark, there are frequently 
cavities found among the cells, which are of severzil 
kinds. Those called receptacles of secretion are 
formed for the reception of the oils and other 
fluids secreted by plants ; as, for example, the 
fragrant oil in the myrtle and the orange, and the 
turpentine in the pine and fir tribe. Other similar 
cavities, called air-cells, contain oxygen nearly in 
a pure state, and are called intercellular spaces. 
All these cavities have no distinct membrane to 
inclose them, but are surrounded by what may be 
called a wall of cells, which form part of the 
cellular tissue. If the stem of the common Hip- 
puris, or mare's-tail, or the leaf-stalk of a water- 
lily, be cut across, a beautiful arrangement of 
these intercellular spaces will be displayed, and 
the manner in which they are formed by the 
peculiar arrangement of the plant's cells is shewn 
in wood-cut b (page 69). 

Cellular tissue readily decays when the parts 
composed of it fall from the plant. In leaves, the 
pulpy parts disappear first, leaving behind the outer 
cuticle and the nerves or veins, which are of firmer 
texture ; the latter, indeed, being composed prin- 
cipally of woody tissue, the tubes of which have 
been filled with earthy matter during the process 
of vegetation, decay very slowly. Those parts of 
a plant which nature seems to have intended not 
to be of long duration — such as the fleshy parts of 
the leaves, the flowers, and the fruit — are composed 
entirely of cellular tissue of loose texture. 

Woo(fy Tissue {Pleurenchytnd). — The stems of 
trees and of flowering-plants in general possess a 
tenacity not found in the leaves and flowers. This 
IS mainly due to the presence of woody tissue, 
which consists of minute spindle-shaped tubes 
lying closely together, and overlapping each other 
at the ends. The strength of these tubes is mainly 
due to the deposit of ligneous matter on their 
inner surface. The value of many plants employed 
in the arts depends upon the abundance of this 
tissue : when separated from the softer tissues of 
the stem and leaves by maceration, it forms the 
fibre of flax, hemp, jute, Chinese grass, and other 
textile substances well known in commerce. In 
cone-bearing plants, such as the Scotch fir, the 
woody tissue is very peculiar, each tube exhibiting 
a series of round discs with a central dot. By 
carefully studying the peculiarities in such tissues, 
the sources of unknown timbers may often be 
determined. In most pines there is a single row 
of discs on each tube, while in others a double 
row of opposite discs is observed. In the Arau- 
carias of the southern hemisphere, the discs are 
angular, and ■ are arranged alternately in several 
rows ; and in the yew, the tube has beautiful 
spiral markings as well as minute discs. Such 

70 



characters are invaluable to the student of veget- 
able palaeontology. 

Vascular tissue has been divided by modem 
botanists into three kinds — namely, vascular 
proper, pitted, and laticiferous. Vascular tissue 
consists of cylindrical tubes of g^eat delicacy and 
thinness, called spiral vessels and ducts. Spiral 
vessels are so called because they contain delicate 
fibres coiled round in a spiral manner. They are 
of a light elastic nature, and their fibres, though 
coiled up naturally like a cork-screw (see fig.), 
may be unrolled to a considerable extent. If a 
leaf-stalk of a geranium or strawberry be cut half 
through, and then doubled down first on one side. 



Spiral VesseL 

and then on the other, and the two pieces be then 
carefully and gently drawn asunder, the trans- 
parent membrane will break, and the spirals will 
unroll so as to appear, when seen with the naked 
eye, like fine hairs between the two portions of 
the leaf-stalk. Spiral vessels prevail in leaves 
and flowers, and are found, though more sparingly, 
in the young greenwood of trees and shrubs ; 
but rarely in the old solid wood, roots, or bark. 
They are few in coniferous trees ; but abundant 
in palms and their allies. In ferns and the club- 
mosses they occur occasionally, but are usually 
replaced by a peculiar kind of vascular tissue, 
called the scalariform tissue, from the ladder-like 
appearance on the angular vessels, caused by bars 
of fibre in their interior ; the other cryptogamous 
or flowerless plants have no vascular tissue. 

Pitted tissue, sometimes called dotted ductSy 
consists of tubes which, when viewed by trans- 
mitted light, appear full of holes. This depends 
on the incrusting matter or cellulose inside being 
unequally deposited over the surface of the mem- 
brane, and thus leaving uncovered spots at various 
intervals. The dotted ducts are larger than the 
vessels of the other tissues. They frequently 
exhibit contractions at intervals, which give them 
a jointed or bead-like appearance. In such 
cases, they seem to be formed of dotted cells 
placed end to end, with the partitions between 
them obliterated, so as to form continuous cylin- 
drical tubes. Laticiferous tissue consists of tubes 
which are distinguished from all other kinds 
of tissue by being branched. They are filled 
with a fluid called latex, of a granular nature, 
often milky or coloured, and exhibiting move- 
ments. This milky fluid abounds in the India- 
rubber and gutta-percha plants, and is seen 
to exude in abundance from the dandelion when 
its leaves or stalks are wounded. The fluid, in 
many plants, contains a large quantity of caou- 
tchouc ; it is bland and nutritious in the cow-tree 
of the Caracas, but in many other plants narcotic 
and acrid. 

Multifarious as are the modifications of the 
tissues of plants, and the cells and vessels of which 
they are composed, all have a common origin, aU 
are modifications of the cell. The plant begins its 
existence as a cell, and its whole course of develop- 
ment may be said to be the evolution of cells. The 
process of cell-development, or cytogenesis, thus 
explains the whole phenomena of plant growth and 
reproduction. To the investigation of this subject. 



VEGETABLE PHYSIOLOGY. 



therefore, the attention of vegetable histolog^sts 
has of late years been specially directed, and the 
results have appeared in the form of certain theories 
which have given rise to much angry discussion. 
There appear to be four modes in which vegetable 
cells are multiplied — namely, by nuclei, by division, 
by gemmation, and by conjugation. 

GENERAL INTEGUMENT AND ITS APPENDAGES. 

Submerged plants have the cells of their leaf- 
tissue directly exposed to the action of the sur- 
rounding water ; but land-plants usually have all 
their organs invested in an epidermis or skin, 
which regulates transpiration, and prevents their 
tissues becoming dried up. The surface of this 
epidermis, again, is covered by a very thin struc- 
tureless layer, called the cuticle. The epidermis 
is composed of cellular tissue; but the cells are 
pressed closely together, and flattened, and they 
are often filled with air instead of water. The use 
of the epidermis is to retain a sufficiency of mois- 
ture in plants; for should the delicate membrane 
of which the cells of their tissue are composed 
become so dry as to lose its elasticity, the different 
organs would be unable to perform their proper 
functions. On this account, its thickness is curi- 
ously adapted to the conditions under which a 
plant grows. Plants of very hot countries are 
supplied with three or even four layers of dense 
external tissue, in order that the moisture may be 
retained, notwithstanding the excessive heat and 
dryness of the climate. But it is necessary that 
the tissues of plants should not be shut out from the 
free action of the atmosphere, whence a large pro- 
portion of their food is derived. They are therefore 
provided with peculiar breathing-pores, or stomata, 
by which air and fluid enter, and from which fluid 
transpires. In mosses, where the leaves usually 
consist of a single layer of cells, stomata are con- 
fined to the fleshy base of the fruit ; but in flower- 
ing-plants they chiefly occur on the under surface 
of the leaf; and this is especially the case in many 
evergreen shrubs, which are thereby enabled to 
benefit by the moist exhalations from the soil and 
herbage beneath, without suffering from a scorching 
sun. This law is reversed where the habits of the 
plant require such an adaptation. Water-lilies and 
other plants whose leaves float on the surface of 
the water or lie flat on the soil, have no stomata 
on their under surface, but are supplied with an 
increased number on their upper surface, which 
alone is exposed to the action of the atmosphere. 
The following calculation of the number of stomata 
in the leaf of the royal water-lily, will serve to 
indicate the extremely minute size of these bodies 
and the great numbers of them required by plants : 
each stomate measures the ^lo^th part of an inch 
in diameter; one square inch of surface contains 
139,843 stomata; so that one ordinary sized leaf 
of this plant, with a surface of 1850*08 square 
inches, contains upwards of twenty-five millions 
of stomata (25,720,937). 

Hairs are minute prolongations from the epi- 
dermis, and are found upon almost every part of 
plants. Sometimes they cover the whole of the 
leaf, and at others they are only found on one 
surface. They are described in general terms as 
downy, silky, hirsute, bristly, ciliate, &c. according 
to their aspect and mode of arrangement The 
hairs of plants are exceedingly variable in size 



and form, and are either unicellular or multicellular 
— consisting of one or of many cells. In either 
case, they may be shnple or branched. There are 
branched unicellular hairs in Crucifera, and beau- 
tiful stellate hairs in many plants. The sting of 
the nettle is a modification of the hair, being a 
conical tube with a basal bulb, filled with irritant 
fluid, which shews singular movements under the 
microscope. The tube is sharp-pointed, and sur- 
mounted by a little curved knob ; when the plant 
comes in contact with the hand, this knob is 
knocked off; the sharp point which it protected 
now penetrates the skin; and the pressure upon 
the conical sting causes the irritant fluid which it 
contains to be poured out into the wound. The 
whole phenomenon is strikingly similar to the 
mode of action of the animal sting. 

Glands. — Although some have stated that there 
is no true process of secretion in plants analogous to 
that of animals, still the latest researches seem to in- 
dicate that such a process does exist, and that it is 
performed by special organs — usually modifications 
of the epidermis itself or of its appendages. Thus, 
in the Cinchonas of South America, we have con- 
ical glands, which pour out a gum-resinous matter 
on their free surface. The same kind of glands 
are found in the bedstraws of our hedgerows. The 
honey of many flowers also appears to be a true 
secretion, poured out upon a free surface of the 
tissue by special cells, which are not analogous to 
the fat-cells of animals, to which the so-called 
vegetable secretions have been likened. 

Besides the above-mentioned organs, there are 
prickles, thorns, and spines. Prickles may be 
called hardened hairs, as they are merely indurated 
expansions of the epidermis, without any woody 
fibre ; and they may be detached from the branch 
which bears them without laceration. Examples 
of prickles are well seen in the rose and bramble. 
Thorns differ from prickles in being formed partly 
of woody fibre ; and they cannot be detached from 
the branch which bears them without lacerating 
its vessels. They have their origin in buds, and 
are the result of an arrestment of development, 
being formed instead of leaves and branches. 
Examples in hawthorn and sloe. Spines resemble 
thorns in every respect, except in being found on 
the leaves and stems of herbaceous plants ; while 
thorns only grow on the trunk and branches of 
woody plants. When spines grow on leaves, they 
are always found on the veins which are extensions 
of the woody fibre. Example, holly. 

ORGANS OF NUTRITION. 

The organs of nutrition are the root, the stem 
and its branches, and the leaves; and of these 
organs, the root and the leaves, or some modifica- 
tion of them, exist in every flowering-plant, as the 
vital functions cannot be carried on without them. 

The root {radix in Latin) is commonly defined 
to be that part of a plant wnich attaches itself to 
the soil where it grows, or to the substance on 
which it feeds, and is the principal organ of nu- 
trition. Exceptions to this definition occur, as in 
the case of some plants which grow floating loosely 
in water, as duck- weed, as well as in the case of 
others having no root at alL As the nourishment 
of a plant is derived from the earth, the root is 
that part which grows in an opposite direction to 
the stem, and is buried in the ground. It is the 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



descending axis, while the stem is the ascending. 
The more common form is the fibrous root as seen 
in grasses, the fibres being terminated by loose 
cells or spongioles, which are the absorbent points. 
But the main root is often thickened into a tap- 
root, giving off secondary fibres — globe-shaped, in 
the turnip — conical, or tapering gradually from the 
collar to the attenuated fibre, in the carrot — fusi- 
form, or tapering at both ends, in the radish — 
abrupt, where the lower end appears as if cut 
off, in the devil's bit scabious. In the dahlia, 
the roots branch off in a fasciculate manner ; 
while in the orchis {O. masculd) they are tuber- 
ous, being in the form of glolje-shaped bodies 
filled with starchy matter. The so-called tuberous 
roots of the potato are merely underground stems, 
from the circumstance of their having eyes or buds 
from which branches will spring. 

The crown, collar, or life-knot, as it is variously 
called, is that part which lies between the stem and 
the root It is the most essential portion of the 
whole; for if it be removed, or seriously injured, 
the plant will die ; whilst the small fibres or root- 
lets, although an essential part of a plant, may be 
destroyed at pleasure, so long as the crown re- 
mains, for it readily reproduces them. When it is 
of a slender make, it dries up as the seeds ripen, 
and the plant soon dies, as seen in the corn-poppy, 
mignonette, and other annuals. 

Roots have a remarkable tendency to grow down- 
wards, or in the direction of the earth's centre ; and 
from experiments, it seems not unlikely that this 
tendency is to some extent an effect of gravitation. 
The precise direction, however, is very much in- 
fluenced by the condition of the soil. Both root 
and rootlets extend as if in quest of food, and will 
penetrate sidewise or obliquely to great distances. 
Though the root and stem differ in many respects, 
yet there are cases where it becomes difficult to dis- 
tinguish between them. Some species of palms send 
down aerial roots for the purpose of strengthening 
their stems, and the same are seen very remarkably 
in the screw-pines and banyans. Many herbaceous 
plants send out roots in a similar manner when 
they are earthed up ; and trees which grow in un- 
natural situations, as on a wall or bare rock, send 
down roots in quest of soil and moisture, which 
afterwards take the appearance of stems. The 
willow, maple, gooseberry, and some other plants, 
may have their roots converted into stems by 
reversing the plants, and burying the tips of the 
shoots in the earth, so as to leave the roots in the 
air. In this case, the branches will soon send out 
fibrous roots from the joints which have been 
buried in the earth, and the fibrous part of the old 
roots withering, the roots themselves will gradually 
assume the character of branches. 

The Stem. — When a plant shews itself above the 
ground, it evidently manifests a strong tendency to 
the light Light, in fact, is essential in bringing it 
to maturity, and in giving the green 
colour to its leaves. The stem, with a 
few exceptions, is always above ground. 
It is divided from the root by the 
part called the crown or collar. The 
space between the collar and the first 
branch is termed the bole or trunk. 
The stem of grasses, corn, and reeds, 
receives the name of culm ; the stem of 
such flowers as the primrose, dodeca- 
theon (see fig.), and the daisy is undeveloped ; 

72 



^ 



hence they are called stemless (acaulescent) ; the 
stalk upon which the flowers are borne being termed 
the scape, or flower-stalk ; the running-stem, as in 
the strawberry and cinquefoil, is termed a runner ; 
a shorter runner that does not root, as in the house- 
leek, is termed an offset; and a small stem pro- 
ceeding laterally from a root or stool, a sucker. 

The stem assumes many forms and characters 
as to bulk, structure, position, place, and dura- 
tion. It appears as a corm (sword-lily, i) ; a 




bulb (the onion, 2) ; a culm (reed, 3) ; or as a 
woody trunk (the oak, 4). When a trunk bears 
permanent or perennial branches, the plant is 
termed a tree; when permanent branches arise, 
not from a distinct trunk, but from near the root, 
the plant is termed a shrub ; and when the whole 
stem is not woody, and dies down every year, at 
least as far as the crown of the root, the plant is 
termed a herb. Trunks which increase by suc- 
cessive layers of new wood on the outside of the 
old, as the ash and beech, are termed exogenous; 
those which increase by the addition of fibrous 
matter in the centre, as the palms, are styled 
endogenous J and those which do not sensibly in- 
crease in thickness, and are formed by the adhesion 
of the leaf-stalks as they spring from the growing 
point, as the tree-ferns, are said to be acrogenous. 
(See Systematic Botany, p. 108, figs, b, a.) 

Buds, which have various forms, consist of the 
young shoots, leaves, or flowers, and proceed from 
what is called the axil of a 
leaf. They are usually formed 
either early in summer or in 1 
autumn, and are so con- 
trived as to preserve from 
injury the delicate structure 
within. The outside is 
composed of tough scales, 
which are frequently cov- 
ered with a gummy resin ; 
and they are internally pro- 
tected by a downy sub- 
stance interposed between 
the leaves. Linnaeus applied the term hyhernacula 
to leaf-buds, being the * winter-quarters ' of the 
young branch. With respect to the manner in 
which the leaves are arranged and folded in the 
bud, which is termed vernation, they may be 
simply placed in apposition, as in the mistleto ; 
plaited, as in the palm and birch ; doubled, as in 
the rose and oak ; embracing, as in the iris and 
the sage ; double embracing, as in valerian and 
teasel ; rolled inwards, as in grasses ; rolled out- 
wards, as in rosemary, primrose, &c. ; rolled 
lengthwise, breadthwise, rolled from the tip to the 
base, or wrapped round the stalk. 




VEGETABLE PHYSIOLOGY. 



Leaves. — Leaves, from their number, position, 
and delicacy of organisation, are designed to effect 
an important office in the vegetable economy. 
Springing from the branches, and exposed in 
profusion to the atmosphere, they perform the 
functions of a breathing-apparatus analogous to 
that of the lungs or gills of animals. A similar 
purpose at least is designed ; for the sap of plants, 
like the blood of animals, requires to be exposed 
to the atmospheric influence, in order that it may 
"be suitable for nutrition. This purpose is accom- 
plished by the agency of the leaves, to which the 
sap, on rising from the roots through the stem and 
branches, is propelled or attracted, and there both 
air and light exercise their beneficial influences. 
Leaves are thus indispensable to the growth of 
plants, and care should be taken not to injure 
them ; for defoliation, either naturally or by art or 
accident, instantly arrests the growth, and the 
failure or diminished expansion of foliage is a 
certain sign of debility. 

A leaf consists generally of two parts — the 




petiole, or leaf-stalk; and the lamina, or blade. 
Sometimes, however, as in the rose tribe, stipules 
(j, s) are attached to the base of the petiole. The 
leaf-stalk {a) is that part which connects the leaf 
with the branch, and at the base will be found 
slightly hollowed, in which a bud rests. Some- 
times the leaf-stalk is wanting, and thus the leaf is 
said to be sessile. In some Australian acacias 
and eucalypti, the petiole is flattened, and occupies 
the place of the leaves. Such petioles are called 
Phyllodia. The lamina, or broad part of the leaf 
{b), is frequently of a different colour on the under 
side. This is exemplified in the common silver- 
weed {Poteniilla anserina), the leaves of which are 
hoary on the lower side, and green on the upper. 
Leaves are either deciduous — falling in autumn — 
or evergreen, lasting till the following season. 
Their forms are exceedingly varied— being simple 
or compound; and these, again, are distinguished 
as oval, lanceolate, cordate, hastate, sagittate, 
pinnate, &c. 

An important character is afforded by the vena- 
tion of leaves — that is, the arrangement of what 
are called their veins. In exogenous or dicotyle- 
donous plants — as our timber trees, for example — 
the leaf is furnished with a strong midrib, from 
which secondary veins diverge, at regular dis- 
tances ; and these, again, branch off into still 
smaller tertiary veins, whose ramifications form a 
reticulation or network in the leaf In endogenous 
or monocotyledonous plants — as grasses and lilies 
— there is usually no distinct midrib, but several 



primary veins, which originate in the base of the 
leaf, and proceed to its apex, being parallel through- 
out. In many tropical endogens, however, there is 
a distinct midrib, from which secondary parallel 
veins diverge on either half of the lamina. In 
acrogens or acotyledonous plants — as ferns— the 
veins are usually arranged in a forked manner. 

The veins of leaves consist of woody tissue, 
accompanied by spiral vessels, the interspaces 
being filled up with the softer parenchyma, or 
cellular tissue. By maceration, the latter may be 
made to disappear, so as to leave merely the veins. 
In aquatic plants, there is a strong tendency to 
non-development of the parenchyma; thus, in 
many of the aquatic crow-foots, the submerged 
leaves consist almost wholly of veins, while the 
floating ones are entire ; but the most remarkable 
instance of this occurs in the Ouvirandra fenes- 
tralis, a water-plant introduced to our hot-houses 
from Madagascar, whose leaves are so destitute of 
parenchyma, that they are, in fact, beautiful lattice- 
like skeleton -leaves. The leaves of the royal 
water-lily are perforated with minute holes at 
regular intervals, and large open spaces occur in 
the leaves of Monstera and Dracontium. 

With regard to the manner in which leaves pro- 
ject from the branches, and their distribution over 
the woody cylinder to which they are attached, 
every possible variety may be observed. They 
may be opposite — that is, two leaves growing on 
either side of the branch, the one directly opposite 
to the other ; alternate, when one leaf springs out 
on one side of the branch, and another on the 
opposite side, a little above it, and so on ; whorled, 
or verticillate, when a number of leaves g^row 
round the stem from a common knot or joint, as 
in the bed-straw. The distribution of alternate 
and opposite, however, is not regular ; for in some 
instances it will be found that the leaves on the 
lower part of the stem are alternate, whilst those 
on the upper are opposite. There are many 
plants which have few or no leaves, but whose 
stems are much dilated, presenting a large super- 
ficies of parenchymatous exterior to the air and 
light — as, for example, in the cactuses. 

Green is the most general colour of leaves, but 
some are red, or purple, or yellow ; some appear 
nearly white, in consequence of being clothed with 
short woolly or silky hair. Leaves are often varie- 
gated, in consequence of the non-development of 
chlorophyll in the cells of certain parts. They 
differ much in substance and structure : some are 
immensely thick and fleshy, as those of the genera 
Aloe and A gave j others remarkably thin, as those 
of the beech. 



ORGANS OF REPRODUCTION. 

The organs of reproduction are the flower, fruit, 
and seeds ; and these, or some modification of 
them, exist in every perfect Phanerogamous or 
flowering-planL 

Flower. — A flower consists of several distinct 
parts — the calyx, corolla, stamens, and pistil. A 
flower is essentially constituted by the presence of 
the last two, which are the sexual organs. When 
there is only one of these present, the plant is 
termed unisexual ; but more commonly these 
organs are both present in the same flower, which 
is in this case termed hermaphrodite. In some 
instances, although the same plant bears both 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



male and female organs, it is not hermaphrodite, 
as these organs occur in different flowers ; in 
others, again, the male and female flowers exist 
only on different plants. Lastly, male, female, and 
hermaphrodite flowers are sometimes found to- 
gether, either on the same or on different plants. 
Sometimes the male or female organs alone, pro- 
tected by a small scale, constitute the flower ; but 
in general they are surrounded and protected by 
the corolla and calyx, which are called the floral 
envelopes. All these are commonly borne on a 
stalk called the peduncle (from pes, pedis, afoot), 
which, expanding at its extremity, forms the re- 
ceptacle, or torus, upon which the whole of the 




a, a, anthers ; d, filament ; i, stigma, or summit of pistil ; e, style ; 
c, ovarj', or seed-vessel ; y, peduncle ; £■, calyx ; A, corolla. 

parts above mentioned are supported. What is 
called the berry in strawberries is nothing more 
than the fleshy receptacle bearing the carpels on 
its surface. 

The calyx (from kalyx, the cup of a flower) is 
the external leafy envelope surrounding the corolla, 
and in which the latter rests as in a cup. Some- 
times it is entire, but more frequently it is divided 
into segments, called sepals, which are more or 
less separated from each other. It is most com- 
monly green, but in some flowers it is coloured. 

The corolla (a little crown) is the conspicuous 
highly coloured part of the flower or blossom, and 
consists of several divisions or leafy parts called 
petals, which are articulated at the base, and con- 
sequently fall off at the earliest manifestations of 
maturity or decay. The variety of tints in the 
flowering part of plants is remarkable. The 
lower part of the single petal of a corolla is called 
the claw, and the broad part is called the limb. 
The corolla is frequently furnished with certain 
secreting organs, attached to the throat or the base 
of the petals, called nectaries. In some plants the 
corolla is absent. 

Stamen (a distaff). — ^Within the beautiful corolla 
are observed several small filaments, arranged in 
a circle around the central parts, and bearing on 
their summit littie oblong bodies ; which are usu- 
ally apparently covered with particles of a fine 
coloured matter like dust These are the male 
parts of reproduction, the stamens, which are 
always next to the petals — that is, between their 
base and the base of the seed-organ, or pistil. 
The number of stamens in each flower varies from 
one to twenty, or more. In length they are equal 
or unequal. In the CrucifercB there are four long 
and two short, and in the foxglove tribe there are 
generally two long and two short. In position, 
they may be opposed to the divisions of the petals, 
or they may alternate with them, which is their 
normal condition. Sometimes they protrude be- 

74 



yond the corolla, at other times they are wholly- 
included within it The filament which supports 
the anther is most commonly straight and filiform. 
On the summit is that essential part the anther 
(from antheros, belonging to a flower), which 
is generally formed of two small membranous 
sacs, or lobes, attached immediately to each 
other, or united by an intermediate connecting 
body. In form, anthers are subject to great 
variety, and, like the filaments, they sometimes 
cohere so as to form a sort of tube, as in the 
CotnpositCE. 

1h!t pollen (fine flour) contained in the anthers 
consists of numerous small bodies, which possess in 
different plants a very different figure, size, and 
colour. The number of these in an anther-lobe 
sometimes amounts to many thousands. In some 
flowers, the pollen-grains are transparent ; in 
others, they are of a white, purple, blue, or brown,, 
and more frequently of a yellow colour ; and they 
often display exquisite markings on their surface,, 
which enable the pollen of certain orders to be 
identified under the microscope. When a grain of 
pollen is dropped into water, it swells, and some- 
times bursts, emitting a minute quantity of granu- 
lar matter, called fovilla, which is the portion 
more essential to fecundation. In orchids and 
some other plants, the pollen occurs in masses, or 
Pollinia. 

Pistil (from pistillutn, a pestle). — The pistil is 
the more or less filamentary body which in most 
plants rises from the centre of the flower terminat- 
ing the axis of growth, and is surrounded by the 
stamens. The pistil represents the female part of 
fructification. Its parts are — i. The ovary, con- 
taining ovules or rudimentary seeds ; 2. The styhy 
or filamentous part ; and 3. The stigma, or en- 
larged club-shaped or cloven part forming the 
apex. The first and last of these ai-e essential,, 
and always present ; but the intermediate one, the 
style, is sometimes not developed, as in the poppy 
and mangosteen. The pistil consists organically 
of one or more carpels (folded leaves), which may 
either be syncarpous (united into one) or apocar- 
pous (separate) ; in the latter case, we have two or 
more pistils in the flower. 

Having thus briefly described the visible repro- 
ductive organs, let us now turn to their functional 
phenomena. When the flower expands, and its 
essential organs have arrived at maturity, the 
anther-valves open and emit the pollen-grains ; 
some of these fall upon the stigma, or terminal 
point of the pistil, where a peculiar tissue, formed 
of papillary or hair-like cells, is ready to retain 
them. A curious phenomenon is now observed. 
The pollen-grain — a single free cell — develops one 
or more tubes from its surface, these being formed 
by its inner membrane, which thus grows through 
the outer one. These tubes are destined to reach 
the ovules at the base of the pistil, and thus to 
carry down from the pollen-grain the matter or 
influence necessary for fertilisation. The tube, 
accordingly, penetrates the soft tissue of the 
stigfma, and passes down the centre of the pistil, 
where a loose conducting tissue is specially formed 
to facilitate its progress. In this way the pollen- 
tube often acquires a length several thousand 
times greater than that of the pollen-cell whence 
it was produced, its nourishment being derived 
from the surrounding tissues which envelop it. 
Mohl regards the development of this filament or 



VEGETABLE PHYSIOLOGY. 



tube as indicating a new analogy between the 
pollen-grain and the spore of cryptogamic plants ; 
for it is, in fact, a process of germination. The 
length of time required for the growth of the 
pollen-tube down to the ovule, is very various in 
different plants, and by no means depends upon 
the length of the style ; thus, in the night-flowering 
cactus, which has a style from eight to nine inches 
long, the pollen-tube reaches the ovules a few 
hours after the pollen has been applied to the 
stigma ; while in the pine, where there is no 
proper style, a whole year elapses before the 
pollen-tubes reach their destination. The lower 
extremity of the pollen-tube ultimately comes into 
contact with the ovule, and enters the foramen 
or micropyle of the latter, so as to reach the 
embryo sac pre-existing there. The result of 
the access of the pollen-tube to the ovule, is 
the production of an embryo in the latter, and 
the ovule, with its contained embryo, ultimately 
ripens into a perfect seed. Fertilisation with 
pollen is essential for the production of fertile 
seeds, although the ovule exists previous to the 
act. Fruits may, in some instances, swell and 
ripen without any process of fertilisation ; but in 
that case, they will not contain seeds capable of 
producing new plants. 

It is not essential for success in this process 
that the pollen should fall immediately from the 
anthers upon the stigma, for we have several 
historical facts which indicate that pollen may 
retain its vitality unimpaired, in the manner of 
seeds. Thus, in the cultivation of the date-tree, 
it is necessary to bring the fruitful plants under 
the influence of the male flowers ; but on one 
occasion, during a civil war in Persia, the male 
date-trees of a whole province were cut down by 
the invading troops, that the fructification of the 
fertile trees might be prevented, and the season's 
crop thus destroyed. But the inhabitants, appre- 
hending such a result, had been careful previously 
to gather the pollen, which they preserved in 
closed vessels, and thus were enabled to impreg- 
nate their trees when the country was freed from 
the destroying enemy. The pollen-grains of the 
date and of the European palm (Chamarops 
hutnilts) are said to have retained vitality after 
the lapse of eighteen years. 

Seed-vessels are various in form — as, for example, 
in the case of the pea {a), the vessel is a legume or 




pod ; in the apple (b), it is a pofne ; and in the 
filbert, a nut. 

All our esculent fruits are in reality so many 
vessels or receptacles for the seeds ; and the 
various forms in which they appear are individ- 
ually suitable to the purposes of their growth. As 
we have already indicated, the seed contains tlic 
embryo, or germ, of the future plant, which is 
generally surrounded by a nutritious substance 



termed the albumen, destined for the support of 
the young plant before its organs are sufficiently 
matured to allow of its supporting itself. This 
albumen varies very much in quantity, sometimes 
being much smaller than the embryo; while in 
other cases, as in the coco-nut, it weighs as many 
or more ounces than the embr>'o does grains. Its 
texture is variable. It is generally fleshy, as in 
the pea and bean ; but sometimes it is farinaceous 
or floury, as in the wheat ; at other times it is oily, 
as in linseed; homy, as in the coffee; or even 
stony, as in the vegetable ivory palm. If the 
embryo consists of one seed-lobe or cotyledon, as 
the wheat, it is said to be monocotyledottous j if of 
two, as in the beech and oak, dicotyledonous — and 
these terms are generally used respectively for 
endogenous and exogenous ; while cryptogamous, 
or flowerless plants, from being propagated by 
spores instead of seeds, are said to be acotyle- 
donoits — that is, without any cotyledon whatever. 

FRUCTIFICATION OF FLOWERLESS PLANTS. 

As already stated, the lowest forms in which 
plants make their appearance are those of the 
cryptogamous, or flowerless orders— such as the 
ferns, lichens, mosses, sea- weeds, and fungi. In 
these, the mode of fructification is very remark- 
able, and quite different from that of flowering- 
plants. They have neither flowers nor proper 
seeds, but are propagated by minute unicellular 
bodies called spores. 

Ferns. — In the ferns {Filices), which are the 
largest and most highly organised of the flowerless 
orders, little brown patches, called sort, may be 
seen on the under sides of the leaves or fronds (see 
figs.). Each of these is composed of a number 





Ferns, shewing the Sori on the back of the Fronds. 

of minute membranous capsules {thecce), which 
contain the reproductive spores, and which are 
often furnished with an elastic ring, for assisting 
in rupturing the spore-case, and thus facilitating tlie 
dispersion of the spores. These spores are not 
the result of a process of fecundation similar to 
what has been described in the case of flowering- 
plants. Impregnation takes place, not upon the 
mature frond, but upon the infant fern, while as 
yet scarcely visible to the naked eye. The spores, 
when scattered over the soil, give rise to minute 
cellular expansions of tissue resembling liver\vorts, 
upon which male and female bodies, called respect- 
ively antheridia and archegonia, are produced. 
The former emit spermatozoids, which move about 
freely, by means of attached cilia. The arche- 
gonia have a central canal, leading down to a 
large globular cell. A spermatozoid enters the 
archegonial canal, reaches the globular cell, and 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




fertilises it. This cell divides, and is soon developed 
into an embryo, with a bud above and a radicle 
below ; and then the circinate fronds shewing the 
genuine fern-structure arise. As an order, ferns 
are very widely distributed, generally consisting 
of a number of leaf-like members called fronds, 
which are the only visible portion of the plant. 
In some species, however, the stem rises above 
ground to the height of thirty to sixty feet, forming 
the well-known tree-ferns of New Zealand and 
tropical islands. 

Fern Allies. — In the horse-tails {Equisetacece) of 
our marshes and ditches, the spores are placed on 
bracteated spikes, terminating the stems. Each 
spore is furnished with two elastic filaments, which 
are coiled around it, and are very hygrometric. 
The horse-tails are herbaceous perennial plants, 
having hollow striated stems, these being either 
simple or branched. In point of size, they are 
now insignificant members of the vegetable king- 
dom ; but geology has revealed the gigantic pro- 
portions they bore in ages long past, when, instead 
of slender stems of a foot or two high, they reared 
their gigantic pillar-like trunks to a height of 
twenty or thirty feet. 
The spores of the pill- 
worts {MarsileacecB) are 
inclosed in little ball- 
like receptacles at the 
bases of the leaves (see 
fig.); the club-mosses 
( LycopodiacecB ) have 
little cone-like spikes 
at the tips of their 
branches, between the 
scales of which occur small spores, while large 
ones occupy the axils of the leaves lower down. 

In the true mosses {Mtisci), the spores are 
inclosed in urn-shaped capsules, which generally 
stand out from the leaves on slender hair-like 
stalks. In the liverworts and lichens there is a 
somewhat similar provision ; and in the algas (sea- 
weeds), the spores are often inclosed in the sub- 
stance of the plant. 

The fungi, or mushroom tribe, are extremely 
diversified in their size, shape, colour, and con- 
sistence. They are entirely composed of cellular 
tissue. The conmion field-mushroom is one of 
the best known, and may be cited as typical 
of the family ; but the mould on cheese, stale 
bread, the mildew on vines, the rust and smut on 
com, and many other minute and yet unobserved 
appearances of a similar nature, are all fungi. 
Their organs of reproduction consist of spores 
variously arranged in different tribes, presenting 
resemblances in some to the lichens, and in others 
to algae. 

There is still much to learn respecting the 
cryptogamic orders, which yearly receive increas- 
ing accessions of students, for it is in these plants 
that the whole vital phenomena of vegetation can 
best be studied. ' We are entirely ignorant,' says 
Professor Lindley, * of the manner in which the 
stems of those that are arborescent are developed, 
and of the course taken by their ascending and 
descending sap — if indeed in them there reaUy 
exist currents similar to those of flowering-plants ; 
which may be doubted. We know not in what 
way the fertilising principle is communicated to 
the sporules or reproductive grains ; the use of the 
different kinds of reproductive matter found in 

76 



most tribes is entirely concealed from us. It is 
even suspected that some of the simplest forms — 
of algae and fungi, at least — are the creatures of 
spontaneous growth : and, in fine, we seem to 
have discovered little that is positive about the 
vital functions of those plants, except that they 
are reproduced by their sporules, which differ 
from seeds, in germinating from any part of their 
surface, instead of from two invariable points.' 

General Economy of Floiverless Plants. — Insig- 
nificant and lowly as the cryptogamia may appear 
to the eye of the common observer, they are 
nevertheless important auxiliaries in the opera- 
tions of nature. It is true that man and his works 
may suffer from their ravages, that mildew, rust in 
corn, and other microscopic forms of vegetation, 
by their rapid increase and destructive effects on 
the substances from which they spring, may cause 
incalculable damage ; but this very scourge pro- 
vides an incentive to intelligent prevention and 
care, while in creation there are no more useful 
scavengers of decaying matter than the fungi. 
In a dry season, for example, and on a favourable 
soil, rust rarely makes its appearance : certain 
conditions are necessary for its development ; and 
it is to obviating these that the farmer must look 
for exemption from this destructive malady in his 
crops. 

It will now be understood that mould is a 
fungus, produced by a previous deposit of germs 
in the tissue or on the surface of the object on 
which it glows. The proximate cause of its devel- 
opment is generally damp, and without this con- 
dition, the embryo remains in a dormant state. 
Still it may be asked, how cheese happens to have 
green mould at its very centre .'' — the reply is, that 
the germs floating in the atmosphere had various 
opportunities of finding admission into this article 
of diet. They may have been deposited on the 
grass of a field ; the grass was eaten by the cow, 
and the germs were so lodged in the milk ; or, 
what is more probable, the germs fell upon the 
curd, and there lay concealed till a certain damp- 
ness in the cheese brought their vegetative powers 
into operation. It is well known that the exposure 
of curd for a day to the atmosphere will have the 
effect of producing cheese liable to mould. A 
fully more surprising instance of fungus vegetation 
in a secluded situation, is that which occurs in the 
fermenting of yeast and other substances. Fer- 
mentation is, in one respect, a chemical process, 
forming a first step towards dissolution ; but the 
action is also vegetative. The whole mass of 
matter gradually assumes the condition of active 
vegetative growth. The fungus germs which had 
been incorporated in the material begin to live 
and expand, each being a plant which grows and 
gives rise to new plants of the same species, until 
the entire fermenting principle is exhausted. 

One great object which nature has in view by 
the germination and dispersion of the algae, mosses, 
and lichens, is clearly that of preparing the way 
for a higher order of vegetation. It cannot pos- 
sibly escape our observation that the tendency to 
vegetate is a power restless and perpetual. We 
hew a stone from the quariy, and place it in a 
damp situation, on the ground or in a wall, and 
shortly a green hue begins to creep over it. This 
is the commencement of a vegetable growth, pro- 
duced by germs floated in the atmosphere ; which, 
being attached at random to the stone, have beea 



VEGETABLE PHYSIOLOGY. 



brought to life through the agency of the moisture. 
Other stones equally exposed, but in dry situations, 
have also received a clothing of these germs, but 
circumstances not being suitable, they have not 
been developed : give the moisture, and they will 
immediately appear. We hew another stone from 
the quarry, and build it into the pier of a bridge, 
just within the surface of the water : shortly, a 
kind of green alga will appear ; but the wet being 
in greater abundance, and more continuous, the 
growth will become more luxuriant than that of 
the terrestrial wall. Instead of the simple green 
coating, we have the addition of long filaments 
resembling hairs {Conferva:), which float and 
accommodate themselves to the water around. 

Nature is incessantly working out vast ends by 
humble and scarcely recognisable means. It seems 
to be a principle that nothing shall remain station- 
airy or unchanged. The whole surface of our planet 
is every instant altering in its features : mountains 
are being washed down into the plains, rocks are 
mouldering into soil, the sea is filling up at one 
place and encroaching on the land at another, 
and water-courses are constantly shifting their 
outlines. The duty of filling up seas, ponds, lakes, 
and rivers, is consigned to diverse means within 
the animal and vegetable economy ; and one of 
these is the growth of algae and other aquatic 
plants. Take a pond of water, and shut off its 
means of supply from rivulets and springs, and 
then observe what an effort nature will make to 
fill it up. The sides and bottom become speedily 
covered with a luxuriant crop of confervae ; other 
plants, which grow only in water, begin to make 
their appearance, their seeds being wafted thither 
by winds ; at length the supei-ficial matting of 
herbage is able to support the weight of birds ; 
there is alternate vegetation and decay ; finally, 
the pond is filled up, and a forest of the highest 
order of trees may in time cover the site of the 
original humble confervas. What, indeed, are the 
extensive peat-mosses but lakes and pools choked 
•with vegetable matter, which remains in a half- 
reduced condition. Thus we see that the green 
alga which giows upon stones in the water, humble 
and apparently insignificant as it is, performs a 
distinct and important part in creation. 

SPECIAL PHENOMENA OF VEGETATION. 

In addition to the ordinary functions of the 
organs, which are common to all plants, there are 
certain anomalous phenomena which cannot be 
reduced to regular laws, and which merit notice 
in this place ; the most remarkable of these are 
the occasional irritability and movements of plants. 

Irritability. — The irritabiUty of animals depends 
entirely on their nervous system ; but as plants 
have no nervous system, their irritability is 
more difficult to be accounted for. The prin- 
cipal phenomena of vegetable irritability may be 
divided into three kinds — namely, those caused 
by atmospheric influence, those depending upon 
the touch of other bodies, and those which appear 
to be perfectly spontaneous. Atmospheric influence 
occasions the closing of the leaves over the extreme 
point of the young shoot at night, as may be 
observed in the chickweed and several other 
common plants. The folding of some flowers in 
the absence of the sun, and the opening of others 
as soon as that luminary has withdrawn its beams, 



are ascribable to a similar cause. The pimpernel 
closes its flowers on the approach of rain. Most 
blossoms expand during sunshine ; but the evening 
primrose, on the contrary, will not open its lai^e 
yellow flowers till the sun has sunk below the 
horizon ; and the night-flowering cereus only 
expands its magnificent blossoms about midnight 
Some flowers are so regular in their hours of 
opening and shutting, that Linnasus formed what 
he called FlorcCs Time-piece, in which each hour 
was represented by the flower which opened or 
closed at that particular time. Solar light is the 
principal agent in producing these phenomena ; 
but in some cases flowers will open by arti- 
ficial light. De Candolle found blossoms expand 
beneath a lamp nearly as well as beneath the sun 
itself; and the crocus and gentian, which close at 
night, will expand as wide as possible when gently 
exposed to the light and heat of a fire. One of 
the most remarkable circumstances respecting the 
effect of atmospheric influences is, that the same 
causes do not affect all plants, and yet no peculi- 
arity of construction has been discovered in those 
that are so affected to distinguish them from those 
that are not 

The irritability produced by external touch is 
a familiar but little understood phenomenon. The 
movements of the sensitive plant are well known ; 
and it is also known that if the ripe seed-vessels 
of the noli-me-tangere be touched in the slightest 
manner, they will open with elasticity, and scatter 
their contents. In the same manner the fruit of 
the squirting cucumber {Elaterium) throws out its 
seeds, and the pulp in which they are contained, 
with violence, and to a considerable distance. 
The stamens of the barberry, when touched with 
a pin, spring forward towards the stigma, after 
which they return to their original position ; while 
the column of the stylidium, which includes the 
style and stamens, and which generally hangs on 
one side, when touched, springs with a jerk to the 
other side of the flower. The most remarkable 
instance of irritabil- 
ity by contact is that 
exhibited by Venus's 
fly - trap {DioncBa 
muscipuld), a native 
of North America. 
The leaves are very 
curiously construct- 
ed. They have broad 
leaf-like petioles, at 
whose extremity are 
two rounded fleshy 
lobes, which form 
the real leaf, and 
which are armed 
with strong spiny 
hairs, three on the blade of each lobe, and a fringe 
of longer ones round the margin. When an 
insect touches the central hairs, the leaf collapses, 
and the insect is entrapped. The leaf generally 
remains closed till the insect is dead. In Sar- 
racenia, or the side-saddle flower, the leaves have 
a pitcher-shaped petiole, which forms a trap for 
flies and other insects, as well as the leaves of 
the Nepenthes, or pitcher-plant, but these do not 
display irritable phenomena. 

The spontaneous movements of plants are etjuaUy 
difficult to be accounted for with those occasional 
by atmospheric phenomena or by external touch. 




a, Leaf of Venus's Fly-trap. 
b, Leaf of Sarracenia. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



It is true that the leaves elongate, the flowers 
expand, the anthers burst, and the seed-vessels 
open spontaneously ; but these are movements 
caused by the progressive development of the 
plant, and subjected to regular laws. The sponta- 
neous movements to which reference is now made 
are quite different — as, for example, those of the 
leaves of Hedysarum gyrans. This plant has 
compound leaves, the terminal leaflet of which 
displays a slight oscillatory motion ; but the side- 
leaflets have such eccentric movements, as to ren- 
der it difficult, if not impossible to explain them, 
and which might appear, indeed, to a fanciful 
mind as though the whole plant were actuated by 
a feeling of caprice. Generally, all the leaflets 
twist and whirl themselves about in an extra- 
ordinary manner, though the air of the hot-house 
in which they grow is perfectly still ; but frequently 
the leaflets on only one side wiU be affected, and 
sometimes only a single leaflet will move, or all 
will become motionless together ; and when this 
is the case, it is quite in vain to attempt to set 
them again in motion by touching them ; though 
sometimes in a moment, after the touching has 
ceased, the leaflets will begin to move again as 
rapidly as before. In hke manner, the side-leaflets 
frequently continue their movements all night, 
while the terminal leaflet remains quietly folded 
up. Cold stops the motion of the leaves, which 
begins again so soon as the heat of the stove in 
which the plant grows is renewed. 

Plants may be deprived of their irritability by 
the vapour of prussic acid, chloroform, or ether. 

Colour. — The colours of plants present many 
points of interest for the consideration of the 
student, and are connected with many important 
phenomena in vegetation. It is to colour, perhaps, 
more than to form, that vegetation, as a whole, 
often owes its importance in the landscape. The 
gay colours of plants usually reside in the corolla, 
the leaves being usually some shade of green ; but 
in the case of sea- weeds and other cryptogams, 
the whole plant is often of a bright red, or green, 
or olive, according to the species, a character 
which has afforded the basis of the classification 
of sea-weeds now in use. 

The green colour of leaves and the gay colour 
of flowers depend upon different kinds of colour- 
ing-matter contained in the cells of the plant, for 
the cell-walls are without colour themselves. In 
the green parts of plants, this colouring-matter is 
in the form of microscopically minute green 
granules of chlorophyll, which are only produced 
under the action of light ; hence plants grown in 
the dark are etiolated. The changes which it 
undergoes, according to its state of oxidation, 
explain the tints which green leaves acquire in 
autumn. The yellow leaves of autumn contain 
proportionately more wax than the green leaves of 
summer, and the yellow rind of ripe fruits more 
than the green rind of unripe fruits. 

The colours of parts not green are due to a 
different kind of colouring-matter, termed chromule, 
whose chemical relations to chlorophyll have not 
been fully investigated. Chromule is usually dif- 
fused throughout the sap of the cells ; as in the 
flower of the tulip, for example, a strip of the 
epidermal tissue of which will shew well, under 
a common compound microscope, the beautiful 
arrangement of cells of different colours, so as to 
give &e general effect seen in this gaudily painted 

78 



flower. In some cases, however, chromule is found 
in the form of distinct granules. The colours of 
flowers are arranged in two series — the cyanic or 
blue, and the xanthic or yellow. A species belong- 
ing to the blue series may exhibit all shades of 
white, purple, and violet, but will not become yellow ; 
and one belonging to the yellow series may exhibit 
all shades of white and orange, but will not become 
pure blue. Both series unite in red. Although 
light is essential to the development of the green 
colour of leaves, its immediate action is not always 
required for the development of the chromule of 
flowers — a fact quite in accordance with the 
practice of florists, who keep their favourite dahlia 
and pansy blooms covered up in their later 
stages. In accordance with this, also, is the 
fact, that flowers grown in the shade are seldom 
different in colour from those fully exposed to the 
air and light. Flowers may be made to change 
their colours by the influence of the soil in a 
most remarkable manner. The petals of the 
common hydrangea, which are naturally pink, 
are said to be made blue by planting the shrub 
in soil impregnated with iron, or providing it 
with charcoal. The change produced in tulips, 
carnations, heart's-eaces, &c. is still more extra- 
ordinary. The flower of a seedling tulip is gener- 
ally unifoiTn ; and after remaining of this colour 
two or three seasons, it will suddenly break, as the 
florists term it, into the most brilliant and varied 
tints of rose, white, yellow, brown, or purple, with- 
out leaving any trace of the original colour. To 
produce this change, florists try a variety of 
means, all of which have relation to the soil ; for 
example, they sometimes keep their tulips in poor 
soil, and then suddenly transplant them into one 
exceedingly rich ; or they reverse the process : at 
other times they change them suddenly from a 
sandy to a clayey soil. Even the chlorophyll of 
plants is often developed under circumstances 
where the influence of light is very slight, and 
would appear to depend in some measure upon 
other agents. Ferns and mosses have been found 
green in mines where they have grown in almost 
total darkness ; and green and red sea-weeds of 
the most brilliant tints grow at great depths in the 
ocean, where the light, being weakened by passing 
through such an immense body of water, can have 
but little colouring effect ■ 

Although it has been stated by Ruskin that 'the 
natural colour of objects never follows form, but is 
arranged on a different system,' the investigations 
of Professor Dickie on the relations between 
colour and form in plants seem to indicate a 
different result. He finds — i. That in polypetalous 
and gamopetalous flowers, of regular form — such 
as the primrose, gentian, and pimpernel — the dis- 
tribution of colour is uniform on the different 
petals, whether free or in cohesion, whatever be 
the number of colours present ; 2. That flowers 
whose form is irregular — as, for example, papili- 
onaceous flowers, where certain petals are larger 
than the others — present an equally irregular dis- 
tribution of colour, whether one or more colours 
be present ; 3. That different forms of corolla, in 
the same head of flowers, often present differences 
of colour ; but all of the same form agree also in 
colour. 

Fragrance. — The cause of fragrance in flowers 
has never yet been fuUy explained. All organ- 
ised bodies consist partly of volatile matters. 



VEGETABLE PHYSIOLOGY. 



and thus we can readily account for the odours 
given out by decaying animal and vegetable 
substances, as they evidently proceed from the 
volatile parts being liberated by decomposition. 
The fragrance of flowers, however, escapes while 
the plants are in a living state, and that most 
abundantly when they are in vigorous and healthy 
condition. Besides the flowers, other parts of 
living plants frequently exhale fragrant odours — 
such as the leaves of the myrtle and geranium, and 
the wood and bark of pines. All these odours pro- 
ceed from oily or resinous matters contained in the 
receptacles of secretion ; but the laws which regu- 
late their liberation, and define their physiological 
uses, are as yet imperfectly known. The odours of 
plants are of three kinds : permanent, fugitive, and 
intermittent. Permanent odours are those given 
out slowly by the plant, not only whilst it is living, 
but also after the fragrant part has been separated 
from the living plant. Of this kind are the odours 
of fragrant wood, of the dried petals of roses, and 
some other flowers. Intermittent odours are the 
most difficult to be accounted for by the vegetable 
physiologist. It is well known that the night- 
smelling stock and several other plants, which are 
entirely devoid of scent during the day, are 
delightfully fragrant during the night. One of 
the orchideous plants produces its powerful aro- 
matic scent only when exposed to the direct rays 
of the sun ; and the flower of the night-blowing 
cereus is fragrant only at intervals during the time 
of its expansion. 

Tastes. — The tastes produced by vegetable sub- 
stances are generally recognised as sweet, acid, 
bitter, astringent, austere, or acrid. As a general 
law, it may be stated that the drier and warmer 
the situation, the- more exposed to light, and the 
slower the growth of any vegetable, liie more 
intense is its peculiar flavour. 

Luminosity, Heat, Electricity. — The luminosity 
of plants — that is, the evolution of light either from 
living or dead vegetable structure — is a rare and 
curious phenomenon. Flowers of an orange colour, 
as the marigold and nasturtium, have been occa- 
sionally observed to present a luminous appearance 
on still warm evenings ; this light being either in 
the form of slight electric-like sparks, or steadier, 
like the phosphorescence of the glow-worm. Certain 
fungi, which grow in warm and moist situations, 
produce a similar phosphorescence ; and decaying 
vegetables, like dead animal matter, have been 
observed to emit the same kind of luminosity. 
This phenomenon seems connected with the ab- 
sorption of oxygen ; and the parts emitting it are 
said to be most luminous when immersed in pure 
oxygen, and cease to emit it when excluded from 
that element. 

The evolution of heat by living plants is a more 
common phenomenon. We are aware that warm- 
blooded ahimals have the power of keeping up a 
certain temperature within them, which varies at 
certain stages of their growth, and perhaps period- 
ically. This result is obtained by respiration — the 
oxygen of the atmosphere uniting with the carbon 
of their blood, and producing a kind of com- 
bustion. A similar, though less understood phe- 
nomenon, seems to take place in the respiration of 
plants. In germination, heat is sensibly evolved ; 
a piece of ice placed on a growing leaf-bud will 
dissolvej when it would remain unchanged in the 
open air ; and experiment has proved that the 



surface of plants is three or four degrees higher 
than the surrounding medium. Again, the internal 
temperature of a lafge trunk is always higher than 
the surrounding atmosphere, and though young 
shoots are sometimes frozen through, the general 
structure both of the wood and bark is such as to 
conduct heat so slowly, that the internal warmth 
is seldom reduced beyond what seems necessary 
to the maintenance of vitality. Generally speaking, 
it may be asserted that plants possess an internal 
vital temperature, and that in the so-called process 
of respiration— the giving off" of carbonic acid or 
oxygen, as the case may be— a certain degree of 
heat is evolved ; but precise experimental results 
are wanting. At the time that the essential organs 
of flowers are fully developed, a certain amount of 
heat is given out. This heat is rapidly carried off" 
by the air, and is therefore not easily detected ; but 
in certain cases, especially in plants belonging to 
the natural order Aracece, the elevation of tempera- 
ture is very marked; the temperature inside the 
flowering spathe varying from io° to 50° F. above 
the surrounding atmosphere. 

The connection of electricity with vegetable 
growth has recently excited the attention of physi- 
ologists ; but little positive information has yet 
been ascertained. It has been long known that 
growth takes place with great rapidity during 
thundery weather; but this may result from the 
nitrogenised products of the shovvers which then 
fall, as well as from the effects of electricity. The 
progressive states of vegetable growth are the 
result of chemical changes ; and as these changes 
are more or less accompanied by electricity, it is 
supposed that plants evolve electricity as well as 
heat. The general electric state of plants is said 
to be negative; and some have attempted to con- 
nect the luxuriant vegetation of the tropics with 
the thunder-storms of these regions, on the sup- 
position that when the atmosphere is positively 
electrified, the two opposite states will give rise to 
such commotions. 

SECRETIONS AND EXCRETIONS OF PLANTS. 

Substances of varied properties are secreted 
by plants, and otherwise formed in their tissues 
according to their respective natures, and their 
healthy or diseased condition at the time of secre- 
tion. Some of these substances are produced by 
the ascending sap; but the greater number are 
deposited by the elaborated or proper juice, and 
consequently are seldom secreted during spring or 
early summer. The intensity of those derived from 
the latter source depends in a great measure upon 
the influence of solar light ; hence they are much 
stronger, and more abundantly produced, in trop- 
ical than in temperate climates. From the manner 
in which many of these are deposited or ejected, 
they appear to be of little or no utility in the 
vegetable economy. Some of them may be re- 
garded as excretions as well as secretions j but 
whether they are to be considered as essential 
components of the sap, or evacuations necessary 
to the healthy condition of the organs, has not yet 
been determined. Being exceedingly varied in 
their properties, they are of great utility to man as 
articles of food, medicine, ornament, and luxury. 

The economical applications of vegetable secre- 
tions and excretions are so numerous, that it would 
be impossible, in our limited space, to enter upon 

79 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



anything like details. It is even difficult to attempt 
any classification of them ; for, though differing in 
their properties and external appearance, many of 
them are identical in chemiccd composition, and, 
subjected to peculiar treatment, readily pass into 
new and singular combinations. Some, for instance, 
are saccharine, as the juice of the sugar-cane. 
Many are oleaginous, balsamic, or resinous ; some 
are narcotic, aromatic, or mucilaginous ; while 
others are astringent, purgative, or poisonous. For 
examples of these divisions, we have such sub- 
stances as palm and olive oil, myrrh, resin, opium, 
camphor, gum-arabic, tannin, gamboge, prussic 
acid, aloes, colocynth, and many others of every- 
day familiarity. 

Besides the proper excretions and secretions, 
there are several adventitious substances found in 
plants, which are not the products of vital organi- 
sation. Lime, for instance, is found in the ashes 
of many plants in union with acids ; sometimes it 
is excreted in the form of a thin crust on their 
leaves, and in other cases in peculiar cells. Silica 
also occurs in considerable quantities, especially 
in the stems of reeds and grasses; it forms the 
glossy pellicle of the cane, and is sometimes found 
in the joints of the bamboo, where it is deposited 
in a soft pasty mass, called tabasheer, which ulti- 
mately hardens into pure semi-transparent silica. 
Equisetum hyemale, called Dutch -rushes, con- 
tains a large quantity of silica, and is used for 
polishing mahogany. Besides these earths, there 
are various metallic oxides and salts, and the well- 
known alkalies — potash and soda. The physio- 
logical uses of such products are but imperfectly 
known. Many of them — such as starch, gum, 
sugar, and the fixed oils — directly administer to 
the support of the young plant and to the forma- 
tion of new tissues. Others, again — such as silica 
and metallic oxides— give hardness and stability 
to the stems and branches; some give elasticity 
and pliancy to the young shoots, thereby prevent- 
ing them from being broken by winds ; and several 
— as tannin, for example — seem to administer to 
the durability of the woody tissue. 

METAMORPHOSES OF PLANTS. 

The metamorphoses of plants, in the general 
sense of the term, form one of the most interesting 
sections of Vegetable Physiology. Technically, it 
is termed Morphology — that is, a consideration of 
the changes and transformations which various 
parts of plants undergo, either from natural or 
artificial causes. We know, for instance, that 
many plants are made to change their appearance 
and qualities by cultivation ; that by grafting, hy- 
bridising, and other means, the gardener can 
change the size, colour, and qualities of his fruits 
and flowers : and that analogous changes take 
place in a state of nature — such as the conversion 
of petals into leaves, and leaves and branches into 
thorns and spines. It is also well known that 
flowers become double by changing their stamens 
into petals ; and it is from a knowledge of such 
facts that botanists have asserted that all the parts 
of the flower and fruit, as well as the appendages 

80 



of the stem or ascending axis, are modifications of 
a single typical organ, and may be considered or 
leaves adapted to special purposes. 

The law which it seeks to establish may be stated 
to be this : that all the appendages of a plant have 
a common origin with the leaf, and may therefore 
successively assume the form and appearance of 
that primary organ. The branches of the stem 
take their origin from leaf-buds, and are clothed 
with branches and leaves by the same process as- 
in the main stem. Towards the point of fructifi- 
cation, the leaves assume the form of bracts ; these, 
again, are succeeded by the leaf-like sepals of 
the calyx; and next by the petals of the corolla. 
Within the petals are the stamens — which some- 
times assume a leafy form — next the pistil, and 
ultimately the seed-vessels. Even the seeds are 
but leaves in another form. Thus, the growth and 
reproduction of plants may be regarded as a circle 
of leaf-like changes, the leaf, or some modification 
of it, being in all cases the organ which administers 
to the functions of vitality. As there is an indubi- 
table passage from leaves to every other organ, so 
may any one organ be found to revert to the 
primary form of the leaf. In the double-flowering: 
cherry, so common in shrubberies, the stamens are 
changed into petals, and the ovary into a greerv 
leaf! 

The hybridism of plants is closely allied to the 
subject of morphology, and is, in fact, a process of 
transformation of an artificial character. As among 
animals two distinct species of the same genus will 
produce an intermediate oflfspring — such as the 
mule, which is the offspring of the horse and ass — 
so among vegetables, two species belonging to the 
same genus can be made to produce a hybrid; 
that is, a new plant possessed of characters inter- 
mediate between its parents. This power of hy- 
bridising is more prevalent among vegetables than 
animals ; for the different species of many genera 
of plants are capable of producing this effect, if the 
pollen of one species be put upon the stigma of 
another. And this crossing may even be applied 
to separate genera. Hybrids have not the power 
of perpetuating their kind like naturally distinct 
species ; for, though occasionally fertile in the 
second and third generations, they have never 
been known to continue so pennanently. But 
though incapable of propagating beyond a limited d 
period, the pollen of the parent species may be I 
made to fertilise them, or their pollen to fertilise 
the parent; but in either case the new offspring 
gradually merges into the original species. Thus 
nature has wisely set a limit to the intermingling 
of species, by which they are preserved from 
ultimately running into confusion and disorder. 
In an economical point of view, hybridism is of 
great value to man. By a knowledge of its prin- 
ciples, he has been enabled to modify the characters 
of natural species, so as to adapt them to his spe- 
cial purposes ; and thus have arisen most of those 
beautiful varieties of what are termed florists* 
flowers, which now adorn the flower-garden. So 
also by crossing varieties of the same species, our 
grains, fruits, and kitchen vegetables have beea 
brought to a high state of perfection. 



SYSTEMATIC BOTANY. 



BOTANY is the science whose purpose it is to 
investigate the Vegetable Kingdom. Vege- 
table Physiology — treated of in the preceding article 
— is that department of the subject which explains 
the organisation and vital functions of plants ; 
Systematic Botany, that which recognises their 
arrangement into groups, according to their form 
and structure. The former relates to functions 
which are common to all vegetables ; the latter 
takes notice only of such peculiarities as serve 
to distinguish one species from another, or one 
family from another family. The vegetable king- 
dom is supposed to contain upwards of 150,000 
species ; and therefore, without some system of 
arrangement into smaller groups and orders, it 
would be difficult to acquire a knowledge of the 
special characteristics of plants, or to convey that 
knowledge to others by any process of description. 
It is the aim of Systematic Botany to obviate this 
difficulty, by classifying plants according to certain 
types and resemblances which are common to a 
number of species ; thus making one description 
equally applicable to a class as to a species. 

The advantages of classification in lessening 
the labour of memory and description, become 
strikingly apparent when we reflect on the diffi- 
culty which would exist were each plant to be 
known by an entirely distinct name. For example, 
there are many species of roses, all of which are 
known by the generic term Rosa, each having 
a second or specific name to designate it separ- 
ately, as Rosa canina (the dog-rose), &c. Now, if 
a botanist hear of a plant called Rosa, though 
its specific name be quite new to him, he has 
instantly a general idea of what sort of plant 
it is, from his previous knowledge of the common 
characteristics which belong to the genus Rosa. 
The principle of classification is to assemble those 
plants which bear most resemblance to each 
other ; and this has been done in different ways 
by different botanists ; each method being called 
the system of the individual who devised it — as 
Tournefort's system, Linnasus's system, Jussieu's 
system. Of the several systems which have been 
suggested, only two are in use at the present time 
— namely, that of Linnasus, the great Swedish 
naturalist (1707-1778) ; and the Natural System, 
in its numerous modifications, that of Jussieu, an 
eminent French botanist, who, during the long 
period between 1789 and 1836, was closely engaged 
in improving the nomenclature and arrangement 
of the vegetable kingdom, having afforded the 
basis of those mostly in use. 

The system of Linnaeus is founded on the sexes 
in plants — the number, situation, proportion, and 
connection of stamens and pistils, which are 
regarded as respectively the male and female 
organs, being chosen to supply characters for the 
classes and orders. This system appears at first 
sight extremely simple, as it depends entirely on 
the counting of so many visible parts ; but it is 
very uncertain, as the number of stamens often 
differs, from accidental circumstances, in plants of 
the same genus ; and it tells nothing of the plant 
but its class and order, which lead only to the 
6 



discovery of its technical name, as plants of the 
most opposite quahties frequently agree in the 
number and disposal of their sexual organs. This 
mode of classification is known among botanists 
as the Sexual System, or the Artificial System, 
because it is founded on mere artificial enumer- 
ation, on a single series of characters, and not 
upon natural qualities or resemblances of the 
plants so arranged. That of Jussieu, on the 
contrary, is founded on the natural affinities ; and 
the botanist who is acquainted with its principles 
can at first sight assign any plant to its proper 
class and order, as there is always a general 
resemblance among the plants belonging to the 
same natural order. Again, knowing the order, 
which is usually typified by some common plant, 
he can predict as to its properties — a species of 
information which the artificial system does not 
attempt to convey. Jussieu's method has been 
greatly improved since the time it was suggested, 
particularly by the late Professor De CandoUe of 
Geneva ; and it is his modification of the original 
plan, with further improvements, which constitutes 
the most generally adopted Natural System of the 
present day. 

According to both systems, plants are divided 
into classes, orders, genera, species, and varieties. 
A class consists of plants resembling each other 
in some grand leading feature, and as strongly 
differing from another class as mammalia do from 
birds, for example. Thus, flowering-plants with 
one cotyledon (or seed-lobe), whose trunks increase 
in thickness from within — as the palm — form a 
distinct class ; while flowering-plants with tvvo 
cotyledons, and whose trunks increase by external 
layers, constitute another class. An order consists 
of plants still more closely allied, so that many 
orders may be found in the same class. Thus, as 
ruminant or cud-chewing animals form an order 
of mammalia, so do the leguminous or pod-bearing 
plants constitute an order of dicotyledonous vege- 
tation. A genus consists of plants so very closely 
allied, that they may be compared to members 
of the same family. The pea, for example, con- 
stitutes a genus of legtiminous plants. Just as sheep 
form a family of the ruminants. A species may 
be compared to one of the members which com- 
pose the family ; thus the garden-pea and sweet- 
pea are different species of the same genus. A 
variety is merely a departure from the common 
appearance of the species in trivial characters, or 
differences which arise from climate, situation, 
greater or less humidity of soil, and other acci- 
dental causes. The boundaries between species 
and varieties are often very vague, some botanists 
regarding those plants as species which others 
consider mere varieties ; but much doubt might 
be removed by attending to the fact, that a species 
reproduces itself from seed, and is always per- 
sistent under the same circumstances, whereas a 
variety has often a tendency to revert to its parent 
species, unless propagated by cuttings, and fos- 
tered by artificial means. A hybrid is a plant 
raised by fecundating the stigma of one spedes 
with the pollen of another— a process which 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



occasionally occurs among plants in a wild state, 
but is more common in cultivation. Unless per- 
petuated by artificial processes, they are liable to 
die out, or revert to their original stock. 

In botanical nomenclature, the name of every 
plant consists of two words ; the first is the name 
of the genus, and the second that of the species 
— as, for example, Qtiercus alba, the white oak. 
When three names are given, the third signifies 
that the plant is a variety ; and this is sometimes 
more strongly marked by using the contraction 
var. before the third name — as, Quercus Ilex var. 
crispa, the curled-leaved variety of the ever- 
green oak. The third name is for the most part 
omitted in botanical catalogues, and the varieties 
indicated by letters of the Greek alphabet — 
observing that the varieties begin with the letter 
/3 — as, Quercus Ilex /3 crispa. 

The primary arrangement of plants, according 
to both the artificial and natural systems, is into 
those with flowers and those without flowers. The 
first division, or that which includes the flowering- 
plants, is distinguished by the name Phanero- 
GAMIA, and in them the organs of reproduction 
are apparent. It comprehends all the trees and 
shrubs used in the economical arts, as well as the 
common ornamental plants of our gardens, and, 
in short, all those that have distinct organs — as 
leaves, branches, flowers, and proper seeds. The 
second division, known by the term Cryptogamia, 
embraces, as the name implies, those plants in 
which the organs of reproduction are not apparent 
— as the ferns, lichens, mosses, and sea-weeds. 
They have no flowers or seeds, in the common 
acceptation of these words, and their fronds or 
leaves are very different from those of flowering- 
plants ; instead of flowers, fruit, and seed, they 
are furnished with little cases or thecce, and in 



these are lodged the reproductive spores, minute 
as the particles of the finest dust. Here the 
resemblance between the two systems ceases — 
their classes and orders being arranged on totally 
different principles. We shall present, in the first 
place, an outline of the Linnasan system, both on 
account of its priority and simplicity, and as an 
initiatory step to gaining a knowledge of the 
different forms of flowers. It is true that it is 
now disused by most men of science ; but for 
the reasons already stated, as well as from the 
fact that many excellent works have been arranged 
on its plan, it is necessary that the general reader, 
as weU as the botanist, should have an acquaint- 
ance with its leading features. 

THE LINN^AN system. 

The sexuality of plants had been discovered 
before the time of Linnaeus ; but as far as is 
now known, he was the first who suggested the 
adoption of this characteristic as a basis of classi- 
fication. According to his system, the vege- 
table kingdom is divided into twenty-four Classes, 
founded upon the number, the proportionate 
lengths, the connection, or the situation of the 
stamens. These classes are again subdivided 
each into one or more Orders, depending upon 
the number of the pistils, the presence or apparent 
absence of a seed-vessel, its shape, or the number 
and connection of the stamens, or on the arrange- 
ment of the florets. Terms compounded of the 
Greek numerals and the word andria, or male, 
are for the most part used to designate the classes ; 
and similar compounds of these numerals, and 
the word gynta, or female, are employed to 
designate most of the orders. The following 
synopsis presents an outline of the system. 



Classes. 

Monandria i stamen . 

Diandria 2 stamens 

Triandria 3 ti 

Tetrandria 4 n 

Pentandria 5 11 

Hexandria 6 « 

Heptandria 7 11 

Octandria 8 n 

Enneandria 9 « 

Decandria 10 

Dodecandria, from 12 to 19 

Icosandria 20 or more 

Polyandria 20 or more 

Didynamia 4 

Tetradynamia 6 



Orders. 

.has 2 — Monogynia and Digynia, or i and 2 pistils. 

. <i 3 — Monogynia, Digynia, and Trigynia. 

. ir 3 — Monogynia, Digynia, and Trigynia. 

. II 3— Monogynia, Digynia, and Tetragynia. 

. II 6 — Mono., Di., Tri., Tetra., Pentagynia, and Polygynia. 

. II 4 — Monogynia, Digynia, Trigynia, and Polygynia. 

. II 4 — Monogynia, Digynia, Tetragynia, and Heptagynia. 

. II 4 — Monogynia, Digynia, Trigynia, and Tetragynia. 

. II 3 — Monogynia, Trigynia, and Hexagynia. 

. II 5 — Monogynia, Digynia, Trigynia, Pentag., and Decagynia. 
7 — Mono., Di., Tri., Tetra., Penta., Hexa., and Dodecagynia. 
3 — Monogynia, Di.-Pentagynia, and Polygynia. 

on the receptacle n 6 — Mono., Di., Tri., Tetra., Pentagynia, and Polygynia. 

2 long and 2 short n 2 — Gymnospermae and Angiospermae. 

4 long and 2 short n 2 — Siliculosa and..Siliquosa. 



on the corolla or calyx n 



Monadelphia, all the filaments united m 8 — Tri., Pent., Hex., Hept., Oct., Dec, Dodec, and Polyand. 



-Pentandria, Hexandna, Octandria, and Decandria. 
II 2— Decandria and Polyandria. 

II 5 — Polyg.-jEqualis, Superfl., Necess., Frustranea, Segregata. 
II 3 — Monandria, Diandria, and Hexandria. 
II 10 — Mona., Di., Tri., Tet., Pen., Hex., Oct., Icos., Polyan., 
Monadelphia. 

DicEcia, stamens on one plant, and pistils on another h 13 — Mo., Di., Tr., Tet., Pen., Hex., Oc, En., Dec, Do., Ifc, 

Polyand., and Monadelphia. 

Polygamia, unisex, or bisex. flowers on same or diff. plants n 2 — MoncEcia, Dioecia. 

Cryptogamia— inconspicuous flowers ,t 5— Filices, Musci, Lichenes, Fungi, Algse. 



Diadelphia, filaments united into two bundles 

PoIyadeli>hia, filaments in three or more bundles 

Syngenesia, five stamens united by their anthers 

Gynandria, the stamens growing on the pistil 

Monoecia, flowers with stam., others with pist. on same plant . 



1. Monandria. — The first 
order of this class contains 
many highly ornamental 
exotics, chiefly herbaceous 
plants, with large leaves and 
showy flowers. Examples — 
turmeric, arrow - root, and 
ginger of commerce. Several 
Monogynia. of the genera are British — as 
Hippuris, or mare's-tail, and 
Centranthus, or red valerian. The second order, 

82 





Digynia. 



Digynia, contains Callitriche, the water-star- 
wort, and Blitum capitatum, the strawberry 
blite. 

II. Diandria. — Flowers with two stamens, and 
with one, two, or three pistils ; thus constituting 
three orders, of which there are upwards of sixty 
genera. The first, Monogynia, contains by far 
the greater number of the genera. Examples — ■ 
the speedwells, olive, fragrant jasmine, lilac, and 
many evergreen shrubs. The rosemary, and the 
numerous species of sage and salvia, are ranked 



SYSTEMATIC BOTANY. 



in this order, though some botanists have sug- 
gested the removal of the latter plant to the class 
DiDYNAMiA, because, in addition to the two perfect 




Trigynia. 



Digynia. Monogynia. 



stamens, there are the rudiments of two others in 
the flower. 

III. Triandria. — Almost all the grasses, 
including the gfrain-bearing cereals, are found 




Trigjmia. 



Dig)mia. Monogynia. 



in this class. The crocus, corn-flag, and iris, and 
many allied foreign genera, also belong to it. 

IV. Tetrandria. — Flowers with four stamens 
of equal length. The ec^ual length of the stamen 
should be specially kept m mind, because the four- 
teenth class (Didynamia) has also four stamens, 
but of these two are longer than the others. Many 
of the genera of this class are beautiful shrubs and 




Tetragynia, 



Digynia. 



Monogjmia. 



trees, chiefly natives of the Cape of Good Hope 
and Australia — as the Proteas, Hakias, Banksias, 
and the splendid waratah or Telopia speciosissima. 
The common pond-weeds {Potamogeton), the 
bed - straws {Galium), and the Lady's - mantle 
{Alchemilla), also belong to this class. 

V. Pentandria. — The curious Stapelia, bear- 
ing flowers of uncommon character both in shape 





Digynia. Monogynia, 

and colour, and moreover diffusing a scent so 




Tetragynia. 



loathsome, that blow - flies lay their eces on 
the petals! The dodder 
{Cuscuta Europaa), the 
elm-tree, the ornamen- 
tal laurustine, the elder, 
the sumach family, the 
Grass of Parnassus, 
pansy, primrose, forget- 
me-not, hemlock, flax, 
potato, and other plants, Pentagynia. 
belong to this class. 

VI. Hexandri A.— Flowers 
with six stamens of equal 
length. By far the greater 
number of our bulbous flower- 
ing and culinary plants — as 
the narcissus, the tulip, the 
lilies, the long-lived Ameri- 
can aloe, the magnificent 
Crinum and Pancratium, the 
pine-apple, the onion, aspara- 
gus, &c. — belong to this class. 

VII. Heptandria.— This class is illustrated 
by the jEscuIus 
and Pavia, better 
known by the name 
horse - chestnuts. 
It is remarkable 
that among above 
3000 genera, so few 
should occur with 
seven stamens. 
The chickweed winter-green {Trientalis Europad) 




Digynia. 




Digynia. 



Monogynia. 





Heptagynia. 



Tetragynia. 



is the only British plant belonging to this class. 

VIII. OCTANDRIA. — The heaths are the most 
conspicuous and numerous examples of the class. 
Of this family alone there are about 550 species 




Trigynia. 



Digynia. Monogynia, 



already described, chiefly nativ^es of the southern 

parts of Africa. Six are found 

in Britain, and several in other 

parts of Europe. The curious 

Rhexia, the day and night 

flowering CEnothera,\he. Fuchsia, 

the Mezereon, the sea-side grape 

and soap-berry of the West 

Indies, the curiously organised 

Bryophyllum, and other genera, 

belong to the class. 




Tetragynia. 



83 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




Monogynia. 



IX. Enneandria. — 
This class includes the 
cinnamon, the laurel, 
the medical and culinary 
rhubarb, the flowering 
rush of Britain {Butomus 
umbellaius), found in 
ponds and ditches in a 
few localities in this 
country. 




Hexagynia. 



Trigynia. 



X. Decandria.— Many of the species of this 




Decagynia. 





Trigynia. 



class are brilliantly flowering plants, such as 
those of the Kalmia, Ledum, 
Rhododendron, Andromeda, Ar- 
butus, Hydrangea, Saxifraga, 
Dianihus (which includes the car- 
nation, pink, and sweet-william). 
Lychnis, Stellaria, Oxalis, and 
Sedum. 

XI. DODECANDRIA. — There isno 
plant yet discovered with eleven 
stamens, and all those of this 
class have the number varying from twelve to 
nineteen. The class includes the mangosteen, 
the garlic-pear, the showy British Lythrum Sali- 




Digynia. 




Pentagynia. 



Tetragynia. 



caria, agrimony. Reseda, one species of which 
(weld) is used by the dyer for producing a yellow 
colour ; while another, R. odorata, is the mignon- 




Monogynia. 
ette, Sempervivum, 



Dodecagynia. 
or house-leek, Asarum or 



Asarabacca, Cephalotus, whose leaves are formed 
into pitchers, like those of the Nepenthes, or 
pitcher-plant. 

XII. ICOSANDRIA. — Flowers having twenty or 
more stamens seated upon the corolla or calyx. 
The situation, and not the number 
of the stamens, furnishes the char- 
acters of the class. It includes 
the roses, the Cactal genera, Cereus, 
Epiphyllum, and Opuntia; the 
myrtle, and its allied genera, 
Eugenia and Eucalyptus, the 
guava, pomegranate, pear, apple, 
quince, cherry, strawberry, rasp- 
berry, &c. 

XIII. POLYANDRIA. — Flowers 
having an unlimited number of stamens, distinct 
from each other, and seated on the receptacle. 
This class comprises, among many others, the 




Monogynia. 




Trigynia. 



Monogynia. 



caper-tree, the poppy, the curious sarracenia, the 
magnificent water-hlies, the Bixa orellana (amotto), 




Polygynia. 



Pentagynia. 



the magnolia, the pasony, the larkspur, the aconite, 
the columbine, the anemone, the buttercups, the 
globe flower, the marsh-marigold, &c. 

XIV. DiDYNAMiA.— The flowers of this class 
are generally ringent ; they have four stamens^ 
two of which are longer than the others. The 
flowers of the fourth class have also four stamens^ 
but these are of equal lengths ; while in this, two 
are long and two short. The calyx also is tubular, 
divided into five or two lipped segments, which 
are unequal and persistent. The corolla is of one 
petal ; the upper lip concave, and sometimes bifid ; 
the lower lip trifid. In the first order, the so- 
called Gymnosperm^, the germander, lavender, 
mint, dead-nettle, and many others of similar 





Angiospennae. 



Gymnospermae. 



character occur. The order Angiosperm^, 
called because, though the stamens are the same 



SYSTEMATIC BOTANY. 



in number and position, the seeds are differently 
disposed, being contained in a more evident 
capsule than the preceding. To this order the 
bignonia, antirrhinum, mimulus, gloxinia, common 
foxglove {Digitalis purpurea), &c. belong. 

XV. Tetradynamia. — Flowers with six sta- 
mens, four of which are longer than the other two. 
Linnaeus divided this class into two orders — SiLl- 
CULOSiE and SlLiQUOS^ — the former being a 
short roundish pod (c), and the latter a long one 
(a). The cabbage, turnip, radish, wallflower, 
stock, rocket, &c. belong to this class. This is a 
truly natural class of plants, forming the order 
Cruciferce of Jussieu ; great similarity of the 
flowers, seeds, &c. being observable throughout 
the whole of the genera. The calyx is four-leaved, 




Stamens and Seed-vessels. 

sepals concave, equal, and deciduous ; corolla of 
four petals, claws inserted into the receptacle, 
limbs widening outwards in a cruciform manner. 

XVI. MONADELPHIA. — The stamens are united 
into one set or brotherhood in this class, which is 
divided into eight orders, founded on the number 




Octandria. Heptandria. Pentandria. Triandria. 

of the stamens, not on that of the pistils, as in 
other classes. In the first order, Triandria, we 
find several beautiful Cape bulbs — as the Tigridia, 
Herbertia, &c. Of the second order, Pentan- 
dria, the passion-flower is the most remarkable. 
There is also the Erodiiim or stork's-bill, a genus 
allied to the geraniums. The third order, Hex- 
ANDRTA, contains but one genus, a bulbous-rooted 

{)lant, called Gilliesia graminea, having grass-like 
eaves and curious flowers. The fourth order, Hep- 
tandria, contains the pelargoniums, commonly 
called geraniums. The fifth order, Octandria, 
having eight stamens, united in one set, contains 
the genus Aitonia, named by Linnaeus in honour 
of the late William Alton, royal gardener at Kew. 
In the sixth order, Decandria, we find the true 
geraniums or crane's-bills. The seventh order, 
Dodecandria, are all tropical plants. In the 




Polyandria. Dodecandria. Decandria. 

eighth order, PoLYANDRiA, are Alihea, Lavatera, 



Hibiscus, Sida, silk-cotton tree, the tea-tree, and 
its magnificent congener, the camellia. 

XVII. DlADELPHiA,— Flowers having two sets 
or brotherhoods of stamens. In general, nine are 




Hexandria, 



Pentandria. 



united together, with a single one by itself, which 
is accounted the second brotherhood. Examples : 
Monnina trifolia; Fumaria, fumitory ; and Po/y- 




Decandria. 



Octandria. 



gala, the milkwort, and many leguminous plants — 
such as the common pea, furze, broom, genista, 
laburnum, rest-harrow, and lupine, 

XVIII. Polvadelphia. — This class contains 
all plants whose flowers have their stamens ar- 
ranged in many brotherhoods. Among the plants 
of this class is the Theobrotna^ which yields 




Polyandria. 



Decandria. 



chocolate. This disposition of the parts on which 
the order is founded, is exemplified in the species 
of Hypericum or St John's wort. 

XIX. SvNGENESiA. — This large class contains 
all the compound or composite flowers which form 
the natural order Composita. The first order is 
^QUALIS, in which all. the florets are hermaphro- 
dite. It contains the sow-thistle, lettuce, hawk- 
weed, burdock, artichoke, &c The second order 




Superflua. 



iEqualis, 



is Superflua, the flowers of which have the 
florets of the disc bisexual, and those forming the 
rays female. This is also a very large order, of 
which tansy, chamomile, helichrysiums, xeran- 
themums, dahlias, &c. are examples. The third 
order is Frustranea, so called because the 
florets of the disc are bisexual, and those in the 
ray or margin neuter. To this belongs the sun- 
flower, the Rudbeckia, Coreopsis, &c The fourth 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



order is Necessaria, because the florets of the 




X^s- y.--r x^ 
Necessaria. 



Frustranea. 



disc, or centre of the flower, being all male, it is 

necessary that those 
of the ray or margin 
should be female, in 
order that there may 
be perfect seed pro- 
duced. Example : 
Calendula. The fifth 
order is called Se- 
GREGATA, because 
the florets have each 
its proper involucre. 
All the plants in this 
order are exotic herbs and under-shrubs, the globe- 
thistle being the most common in British gardens. 
XX. Gynandria. — This class contains plants 
which have their stamens seated upon the pistiL 
The class is divided into three orders ; the first, 




Segregata. 




Hexandria. Diandria. 



Monandria. 



Monandria, having one anther seated on the 
pistil, and comprises Orchis, Ophrys, Epipactis, 
&c. In the second order, Diandria, the flowers 
have two anthers on the pistil ; to this belongs 
the ladies'-slipper. The third order, Hexan- 
dria, containing plants which have six stamens 
seated in the pistil, has only one genus — namely, 
the Arhtolochia, or birthwort. 
XXI. MONCECIA. — This class (meaning one 





Diandria. Monandria. 

household) consists of plants which have male and 





Triandria. 



88 



Monandria. 



female flowers separate, but on 
the same root — such as the 
bread-fruit tree, the Zannich- 
ellia palustris, the maize or 
Indian corn {Zea), the box, the 
mulberry, the common nettle, 
the Aucuba japonica, the Ama- 
ranthus, the coco-nut and other 
palms. Begonia, the chestnut, 
beech, hazel, walnut, oak, pines 
and firs, larch, cedar, cypress, 
gourd, melon, and cucumber, 
the poisonous manihot, the 
castor-oil, and the cuckoo-pint 
or wake-robin (Arum tnacul- 
atuni). There are ten orders, 
distinguished by the number 
and arrangement of the sta- 
mens, &c. some of which are 
illustrated in the wood-cuts. To 
this class belong the Carices 
or sedges, and aJso the Erio- 
caulon septattgulare. 




Triandria. 




Monadelphia. 

XXII. DiCEClA. — This class is composed of 
plants which have unisexual flowers, not on the 
same, but on different individuals, such as the 
screw-pine, the willow, poplar, crow-berry, date- 
palm, candle-berry myrtle, sweet gale, spinach, 
mistleto, hop, hemp, &c. The orders are dis- 
tinguished by the number, &c. of the stamens, as 
indicated in the following wood-cuts : 




SYSTEMATIC BOTANY. 






Enneandria. 



Octandria. 



Decaudria. 






Polyandria. 



Icosandria. 



XXIII, PoLYGAMiA. — The class Polygamia (a 
word signifying many marriages) contains plants 
having both unisexual and bisexual flowers on the 
same or on different individuals. There is con- 
siderable uncertainty about the arrangement of 
this division, because some of the genera are not 
always constant in their modes of flowering; and 
even single plants wiU occasionally exhibit all the 
characters by which the different orders are dis- 
tinguished. Here are the mimosas, the acacias, 




Dioecia. 

the maples, the Ailantus, the mango, some palms, 
the anacardium, and the figs. 

XXIV. Cryptogamia. — The class Crypto- 
GAMIA (a term signifying hidden marriages) con- 
sists of the flowerless plants corresponding with 
the class of the same name in the natural system. 
It is illustrated by ferns, mosses, lichens, fungi, 
and sea-weeds. 



THE NATURAL SYSTEM. 

* The Natural System of Botany,' says Dr Lind- 
ley, ' being founded on these principles — that all 
points of resemblance between the various parts, 
properties, and qualities of plants shall be taken 
into consideration; that thence an arrangement 
shall be deduced in which plants must be placed 
next each other which have the greatest degree of 
similarity in these respects ; and that consequently 
the quality of an imperfectly known plant may be 
judged of by that of another which is well known 
— it must be obvious that such a method possesses 
great superiority over artificial systems, like that 
of Linnaeus, in which there is no combination of 
ideas, but which are mere collections of isolated 
facts, having no distinct relation to each other. 
The advantages of the Natural System, in applying 
botany to useful purposes, are immense, especially 
to medical men, who depend so much upon the 



Monadelphia, 

vegetable kingdom for their remedial agents. A 
knowledge of the properties of one plant enables 
the practitioner to judge scientifically of the quali- 
ties of other plants naturally allied to it; and 
therefore the physician acquainted with the natural 
system of botany may direct his inquiries, when 
on foreign stations, not empirically, but upon fixed 
principles, into the qualities of the medicinal plants 
which have been provided in every region for the 
alleviation of the maladies peculiar to it. He is 
thus enabled to read the hidden characters with 
which Nature has labelled all the hosts of species 
which spring from her teeming bosom. Every one 
of these bears inscribed upon it the uses to which 
it may be applied, the dangers to be apprehended 
from it, or the virtues with which it has been en- 
dowed. The language in which they are written 
is not indeed human: it is in the living hiero- 
glyphics of the Almighty, which the skill of man is 
permitted to interpret. The key to their meaning 
lies enveloped in the folds of the natural system, 
and is to be found in no other place.' Such a 
system as is here eloquently delineated, we aim at 
rather than possess. All the modifications — and 
they are neither few nor unimportant — of Jussieu's 
original plan which have been promulgated, are 
merely contributions to one great end ; and years 
of patient research, crowned by the most extensive 
powers of generalisation, must elapse before botany 
can boast of a perfect system. 

According to the original system of Jussieu, all 
the known plants were arranged into a hundred 
Orders, beginning with the Fungi, and mounting 
upwards to the Conifercej and 3iese Orders were 
divided into three great Classes — namely, the 
ACOTYLEDONES, or plants without any cotyledon or 
seed-lobe; the MONOCOTYLEDONES, plants with one 
cotyledon; and the DicOTYLEDONES, those with 
two or more cotyledons. The Acotylcdonous plants 
were not subdivided ; but the Monocotyledones 
were arranged into sub-classes, according as the 
stamens were hypogynous, or arising from under 
the pistil ; perigynous, or growing from the calyx ; 
and epigynous, or arising apparently from above 
the ovary by adhesion to it. The Dicotyledones 
were divided into the apetalous, or those without 
petals; the monopetalous, those with one petal; 
and the polypetalous, those with several separate 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



petals ; and these again were subdivided, according 
to the position of the stamens with regard to the 
pistil, in the same manner as the Monocotyledonous 
plants. To these were added what Jussieu called 
Duiines, or those plants with separated unisexual 
flowers. The fault of this system, like that of 
Linnaeus, was that it associated species dissimilar 
in their nature; the classification depending on 
one peculiar feature more than on the general 
appearance, qualities, and habits of the plant. 

The system of Jussieu was improved by De 
CandoUe, who at first made i6i orders; but these 
were afterwards greatly increased, and Lindley 
enumerates upwards of 300. 

The first grand division of De Candolle, like 
that of Linnaeus, is into the Flowering and Flower- 
less plants, which he designates respectively the 
Vasculares and the Cellulares. This division, how- 
ever, is not absolutely correct ; for although all the 
flowering-plants contain vascular tissue, and the 
flowerless consist principally of cellular tissue, yet 
scalariform or ladder-like vessels are common in 
the ferns and club-mosses. The Vasculares and 
Cellulares of De Candolle may be considered as 
equivalent to the Phanogamia and Cryptogamia 
of the older botanists. 

His second division depends upon the cotyledons 
of the embryo; and, like Jussieu, he divides the 
flowering-plants into Dicotyledones, or those 




with two or more cotyledons or seed-leaves, as a ; 
MONOCOTYLEDONES, those which have only one 
seed-leaf {b, b) ; and Acotyledones, those having 
no seed-leaf, and, in fact, no proper seeds — such 
as the Cryptogamia. The dififerences between 
these three divisions are decided, and are exhibited 
in different parts of the plant ; but they are partic- 
ularly conspicuous in the leaves — the venation of 




Dicotyledonous leaves being reticulated, as in the 
apple (a); and that of Monocotyledonous being 
chiefly in parallel lines, as shewn in the leaf of the 
Gloriosa {g\ Dicotyledonous trees are said to be 
Exogenous, from the fact of their trunks increasing 
by external layers ; Monocotyledonous onts,Endog- 
enous, on account of the enlargement taking place 
from within ; and Acotyledonous trees, Acrogenous, 
because the increase takes place only at the top or 
growing-point. 

Dicotyledonous plants are divided into the 
DichlamydecE, or those with two floral envelopes — 

88 



that is, having a separate calyx {a) and corolla {b)\ 
and the Monochlamydece, or those having only one 




floral envelope, which is always called the calyx, 
as in the detached floret in the wood-cut \c). 





These distinctions, however, are not always inva- 
riable, as many plants in the first division have no 
corolla, but simply a coloured calyx. 

The DichlamydecB are further divided into three 
sub-classes : L Thalamijlorce, in which the sta- 
mens and petals are all inserted in the receptacle 




Vine: 



a, bunch of flowers ; b, flower before expansion ; c, flower expand- 
ing ; d, stamens and ovary ; e, vertical section of the ovary ; f, 
fruit ; g, horizontal section of the ovary ; h, vertical section of 
the fruit, shewing the position of the seed. 

{hypogynous), as represented in the accompanying 
dissection of the common vine. II. Calyciflorce, 
in which the stamens and petals are perigynouSf 




Acacia : 
a, calyx ; h, corolla ; c, flower ; d, seed-pod open. 

inserted in the calyx, as shewn in the preceding 
dissection of an Acacia j or epigynous, arising from 
the upper part of the ovary. III. Corolliflorce, in 



SYSTEMATIC BOTANY. 



which the stamens are inserted on the petals, as 
in the annexed dissection of the acanthus, or in a 




Acanthus ; 



«, corolla opened, shewing the .stamens and pistil ; i, one stamen ; 
c, pistil ; d, ripe seed-vessel, covered with its calyx and bracts ; 
e, seed-vessel burst previously to shedding its seeds ; y, seed 
opened, shewing the radicle and plume. 

few cases on the receptacle, the parts of the corolla 
being united together. The Monochlamydece are 
those having only one, or sometimes no floral 
envelope. 

Monocotyledonous plants are divided into those 
with p>etals, called Petaloidees, and those with 
glumes, as grasses, Glumiferce. 

Floiverless or Cryptogamous plants are divided 
into two classes — those formed of a cellular ex- 
pansion without distinct stem or leaves, which are 
called Thallogens (a) ; and those with leaves 
(fronds) borne upon a distinct stem or rhizome, 
Acrogens {b). 




Cryptogamous Plants. 

The distinctions between the orders are drawn 
from the number and arrangement of petals, 
sepals, and stamens ; the construction of the 
anthers, and the manner in which they burst ; the 
structure of the seed-vessel and of the seeds, with 
the position of the embryo ; the position of the 
leaves, whether alternate or opposite, or with or 
without stipules ; and the general habits and pro- 
perties of the plants. 

Having thus explained the basis of arrange- 
ment, we shall now proceed to consider the 
Orders — premising that while the whole are 
tabulated, our space will only permit us to 
detail the more interesting and important ones. 
This, however, we shall endeavour to do in such 
a manner as may at once present an outline of 
the System, and render the reader familiar with 
the phraseology and plan of procedure. 



In this and the subsequent lists of natural 
orders, those orders marked with an asterisk con- 
tain species indigenous in Britain. 

EXOGENOUS OR DICOTYLEDONOUS 
PLANTS. 

^ THALAMIFLORiE. 

Chlznacez— ChUenads. 
TemstrOmiacex — Tea order. 

Olacaceic — OUut order. 

Icacinaceae — Icacina order. 

Cyrillaceac — Cyrilla order. 

Aurantiacez — Orange order. 
•Hypcricacea;— St John's worts. 

Gu uifera:--Guttifer». 

M arcgra viacesc— M argraviads. 

Hippocrateacex — Hippocra- 
teads. 

Malpighiaceae— Malpighiadt. 

Erythroxylea; — Redwoods. 
• Aceraceae — M aples. 

Sai>indaccae — Soapworts. 

Rhizobolacea;— Suwarrow-nut». 

Meliacea: — Meliads. 

Humiriaccs — Humirium order. 

Cedrelacese — Mahogany order. 

Vitaceae— Vineworts. 
*Geraniaceae— Crxmes'-biUs. 
•Linaceac — Flaxworts. 
•Oxalidacex — Wood-sorrels. 
*Balsaminaceae— Balsams. 

TropaeolacesE — Indian Cresses. 

Limnanthaceae — Limnanthids. 

Pittosporaceae — Pittosporum or» 
der. 

Brexiaceae— Brexia order. 

2ygophyIlacea:— Bean-capers. 

Rutaceae — Rueworts. 

Xanthoxylaceae — Prickly-ash or- 
der. 

Ochnaceae — Ochnads. 

Simarubaceae — Quassia order. 



* Ranunculaceae — Crowfoots. 
Dilleniaceae— Dilleniads. 
Magnoliaceae — Magnoliads. 
Anonaceac — Anonads. 
Schizandraceae — Schizandra or- 
der. 

Menispermaceae — Moonseeds. 

Lardizabalaceae — Lardizabala 
order. 
*Berberidaceae — Barberry order. 

Cabombaceae — Watershields. 
•Nymphaeaceae— Water-lilies. 

Nelumbiaceae — Water-beans. 

Sarraceniaceae — Water-pitchers. 
"Papaveraceae — Poppy order. 
*Fumariaceae — Fumeworts. 
•Cruciferae — Crucifers. 

Capparidaceae — Capparids. 
♦Resedaceae — Weldworts. 

Flacourtiaceae — Amotto order. 
*Cistaceae — Rock-roses. 
*Violacea5 — Violets. 
*Droseraceae — Sun-dews. 
*Polygalaceae — Milkworts. 

Krameriaceae — Rhatany order. 

Tremandraceae — Poreworts. 
*Tamaricaceae — Tamarisks. 

* Frankeniaceae — Frankeniads. 

* Elatinaceae — Water-peppers. 
*Caryophyllaceae — Cloveworts. 

Vivianiaceae— Viviania order. 
"Malvaceae — M allowworts. 

Sterculiaceae — Silk-cottons. 

Byttneriacese — Chocolate order. 
*Tiliaceae — Lindenblooms. 

Dipteraceae— Dipterads. 



RANUNCULACEiE.— The plants constituting this 
order are herbs, or rarely shrubs, with generally 
deeply cut, rarely stipulate leaves, and stem-clasp- 
ing petioles. The majority of the species are 
hardy, and abound in an acrid poisonous juice, as 
is well exemplified in the common buttercups of the 
meadows, belonging to the genus Ranunculus, from 
which the order takes its name. The plants of the 
order are very variable in their flowers ; many of 
them having merely one floral envelope, and others 
having a coloured calyx, with only very small and 
inconspicuous petals. When the flowers are regu- 
lar — that is, when the parts are all of one size — 
the corolla consists generally of five petals, and 
the calyx of five sepals, though the number of the 
petals sometimes varies from three to fifteen. 
There are numerous stamens which grow from 
beneath the pistil, and are always separate, having 
their anthers bursting outwardly. The seeds are 
for the most part contained in carpels which are 
separate. The embryo is very small, and placed 
at the base of the albumen, which is either fleshy 
or bony. In consequence of the variable character 
of their flowers, the Ranunculacece are somewhat 
perplexing to the learner, though they may be 
generally known by their numerous distinct sta- 
mens springing from below the pistil, and by their 
distinct carpels, which frequently grow in several 
whorls round an elevated receptacle, as in the 
crowfoot and pheasant's-eye. The calyx generally 
falls off with the petals, but in the pasony it 
remains till the seed is ripe. The carpels are in 
many cases only one-seeded, and are sometimes 
winged, as in the anemone and clematis, in order 
to scatter the seeds, as the carpels in this case 
do not open naturally, but fall with the seed. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Sometimes, however, the carpels are many-seeded, 
and open naturally when ripe, as in the paeony, the 
larkspur, the columbine, &c. The principal genera 
— which lie within the examination of every one — 
are the Ranunculus and Paeony, having regular 
flowers and two floral envelopes ; the Anemone, 
the Hepatica, the Christmas Rose, and the winter 
Aconite, which have regular flowers, but generally 
only one floral envelope; and the Larkspur, 
Monkshood, and Columbine, which have irregular 
flowers. The Clematis is one of the few shrubby 
plants belonging to the order ; it has regular 
flowers, and generally only one floral envelope. 
The RanunculacecB are of little economical import- 
ance. The juice of the whole order is acrid, the 
roots of many intensely bitter, and the bark of a 
few tonic and bitter. The seeds of the Nigella 
are aromatic, and were formerly used as pepper ; 
but those of all the other genera are poisonous, 
unless husked. The flowers of some are objects 
of great beauty — as the larkspurs, ranunculuses, 
anemones, paeony, and columbine. The 'lesser 
celandine of Wordsworth {Ranunculus Ficarid) 
has been used as an article of food in Austria, its 
small farinaceous tubers resembling peas. But 
most of the plants belonging to the order are 
acrid and poisonous, some of them eminently so. 
Ranunculus arvensis is one of the most dangerous 
farm-weeds which the agriculturist has to fear ; 
but the monkshood {Aconitum Napellus) exceeds 
them all in virulence, and has been the cause of 
distressing accidents, from its root being mistaken 
for horse-radish. We read in classic story how 
the Roman stepmothers of old employed this root 
to poison their adopted children ; and a nearly 
alHed species has derived notoriety from having 
been employed by the Nepaulese to poison their 
wells against the approach of an enemy. 

DiLLENiACEiE. — This order consists of woody 
plants having astringent qualities. Some of them 
yield excellent timber. They are chiefly confined 
to Australasia, India, and equinoctial America. 

Magnoliace^e. — This order consists of woody 
plants remarkable for the beauty of their foliage 
and the fragrance of their flowers, of which the 
common Magnoha of gardens is a familiar ex- 
ample : they have bitter, tonic, and aromatic 
qualities. Winter's Bark {Drimys Wititeri), and 
the tulip-tree of America {Liriodendron tuliptferd), 
belong to the order. 

Berberidace.«. — Plants of temperate and warm 
countries in both hemispheres, represented in 
Britain by the common barberry of our hedgerows, 
the stamens of which display irritability when 
touched near the base. According to the late Sir 
J. Y. Simpson, the roots of several species furnish 
the astringent matter called Lycium by Dios- 
corides. Berberis dulcis yields a table-fruit. 

Nymph^ace^. — Gigantic aquatic herbs, with 
a thick rhizome in the mud, giving off" large float- 
ing leaves on long petioles. The rhizomes exhibit 
a structure resembling that of endogenous plants ; 
but the embryo is truly dicotyledonous. Water- 
lilies appear to occur in most parts of the 
world, except cold regions. The white water-lily 
{NymphcEa alba) is one of the greatest ornaments 
of the English and Scotch lakes ; while the yellow 
one {Nuphar luted) more commonly occurs in 
slow streams, and pools. N. pumila is rare. 
The most magnificent of aU is the Victoria regia, 
the royal water-lily of South America, whose size, 

90 



in keeping with the gigantic proportions of the 
Amazons and Essequibos, on whose waters it 
displays its beauty, is unrivalled in the vegetable 
kingdom. Its floating leaves are two yards across, 
continuously covering miles of surface with their 
verdure, each having a tumed-up margin like a 
tea-tray. The flowers are a foot across, formed 
of hundreds of petals of the most delicate rose- 
colour, and exhale a deUcious perfume in the 
evening as they expand. 

PAPAVERACEiE. — This order consists of very 
handsome herbaceous plants, annual and peren- 
nial, most of which are natives of the temperate 
parts of Europe and Asia. The leaves are alter- 
nate, sometimes deeply cut, and without stipules. 
The flowers are solitary, elevated on long pe- 
duncles, showy, and usually white, yellow, or red ; 
and the bud in all, except the large scarlet Eastern 
poppies, is shrouded in only two sepals, which fall 
off as soon as the flower expands. The Oriental 
species have three sepals, and one of them {Pa- 
paver bracteatum) has two large bracts which 
remain after the flower has expanded, and form a 
kind of calyx, though the real calyx has dropped 
off". There are generally four petals, or a mul- 
tiple of four, which are crumpled in the bud, and 
soon fall off. The stamens are very numerous, 
inserted in four or more whorls beneath the pistil 
{a). The ovary is solitary, forming a capsule, 
which consists of several carpels grown together ; 
stigmas generally 
stellate on the flat 
apex of the ovary. 
Notwithstanding the 
fleshy ovary, the fruit 
is a dry capsule, with 
only one cell, the 
divisions between the 
carpels having dis- 
appeared. The seeds 
are numerous, have 
a minute straight em- 
bryo, imbedded in 
albumen, and be- 
come loose in the 
capsule when they 
are ripe. Before the 
seeds are ripe, the 

walls of the capsules ^ ., 

, L J Papaver somniferum. 

become as hard as a ^ 

shell ; and the stigmas, which are grown together, 
and become equally hard, form a star-shaped lid 
for the capsule {b). Under this there is a set 
of valves that open for the discharge of the 
seed. 

The British genera are — Papaver, the poppy, of 
which there are five native species ; Meconopsis, 
Welsh poppy ; Glaucium, horned poppy ; Cheli- 
donium, greater celandine or swallow-wort. There 
are many more, however, grown in our gardens as 
ornamental plants, such as Sanguinaria, or blood- 
root ; Argemone, the prickly poppy; Eschscholt- 
ziaj Roemeriaj Hypecoum ; Platystemon; and 
Platy stigma. In the homed poppy, the seed- 
vessel is formed of two carpels grown together, 
which look like a pod ; and when ripe, from their 
length and stiffness, bear a considerable resem- 
blance to a horn ; hence the name. The Sangui- 
naria has a red juice ; the greater celandine, as 
well as the prickly poppy, has a yellow juice — the 
juice of the others is white. In the Eschscholtzias 




SYSTEMATIC BOTANY. 



the sepals do not separate ; but becoming detached 
at the base, they retain the shape of a hood or 
extinguisher, till pushed off by the expansion of 
the corolla. The capsules of the Eschscholtzias 
are elongated, and are easily known by the large 
fleshy projection at their base. The plants of the 
order are easily detected by their general resem- 
blance to each other, especially in their flowers. 

All the Poppyworts abound in a thick glutinous 
juice, which poisons by stupefying. All parts of 
the plant furnish more or less this milky sap, but 
the main supply is derived from the unripe seed- 
vessels. When in a green state, those of the large 
white poppy {P. somniferum) are slightly wounded 
with a knife, which causes the juice to exude freely ; 
and on exposure to the air, it concretes or becomes 
inspissated. In this state, it forms crude or lump 
opium, which, dissolved in spirit of wine, and 
filtered, produces the laudanum of the shops. 
Chemically, opium consists of an insoluble gum, 
a small quantity of resin, and caoutchouc. Its 
effects on the animal system depend upon two 
alkaline principles which it contains — namely, 
morphia and narcotine ; the former producing a 
sedative, and the latter a stimulating effect. It is 
curious that the seeds possess none of the stupe- 
fying properties of the plant, but are mucilaginous 
and oily, and may be eaten with impunity. The 
seeds of one species, however {Argemoni Mexi- 
cana), are said to be narcotic, especially when 
smoked ; but it is probable that in this case the 
opiate resides in the coating of the seed rather 
than in the albumen. 

Crucifer^. — This is one of the most extensive 
and important of the natural orders. Most of the 
genera are herbaceous annuals and perennials. 
The leaves are alternate, and the flowers are pro- 
duced in corymbs or racemes, 
being usually regular, with a calyx 
of four sepals, and a corolla of 
four petals, disposed in the form 
of a Maltese cross : hence the 
name Crucifera, or cross-bearing. 
There are six stamens, two much 
shorter than the others, as shewn 
under the Linnaean class Tetrady- 
namia. The pods open naturally 
when ripe, the valves curling outwards, as in the 
common cabbage or wallflower, for example. The 
seeds have no albumen, and the cotyledons are 
curiously folded down on the radicle. There can 
be no difficulty in recognising a cruciferous plant 
when it is in flower, by the cross form of its corolla, 
as in the preceding figure, and its six stamens, two 
of which are shorter than the others. 

Among the more common genera may be men- 
tioned Brassica, including the cabbage and turnip 
Cheiranthus, the wallflower ; Mathiola, the stocks 
Iberis, the candy-tuft ; Isatis tinctoria, the woad 
Artnoracia, the horse-radish ; Sinapis, the mus- 
tard ; Raphanus, the radish ; and many other well- 
known plants. The plants are generally distributed, 
but abound in cold and temperate regions. There 
are about 1700 known species. 

The properties of the Crucifers are antiscorbutic 
and pungent, combined with an acrid flavour ; and 
the seeds of many abound in a fixed oil : properties 
of which the common cress, mustard, and rape 
may be taken as examples. Most of them form 
articles of human food, and are valuable not only 
for their antiscorbutic properties, but from the 




Crucifer. 




Marsh-mallow. 



fact that they contain a large amount of nitrogen. 
All the cultivated varieties of turnip appear to 
have been derived from Brassica Rapa. which 
occurs in a wild state in Britain. 

Malvacel«.— All the plants belonging to this 
natural order bear a strikmg resemblance to each 
other, and have large showy flowers. The petals and 
sepals are each five in number, but the calyx has 
three bracts on the outside, having the appearance 
of a second calyx below the true one. Estivation 
twisted. The most remarkable part of the flower is 
the central column, and this is so decided, that a bot- 
anist is always able to re- 
cognise one of the Mal- 
vaceae at first sight. This 
column is formed by the 
filaments of the stamens 
growing together, so as to 
leave only a small portion 
just below the anthers 
free, as is seen in the 
flower of the marsh-mal- 
low — the lower portion 
forming a tube round the 
pistil. The anthers are 

one-celled, kidney-shaped, and burst transversely^ 
opening inwardly. This peculiar construction of the 
stamens may be observed distinctly in the mallows,, 
the hollyhocks, and, in short, in all the genera 
belonging to the order. The styles also grow 
together, as may be seen when the stamens are 
removed ; and the carpels, which are of the same 
number with the styles, form what children call 
'mallow cheeses.' The carpels are one or many 
seeded, sometimes closely united, sometimes separ- 
ated or separable ; fruit capsular or baccate. Most 
of the species are herbaceous plants ; several, trees 
or shrubs. Leaves alternate, more or less divided 
and stipulate, often covered with stellate hairs. 
The plants abound in tropical regions and in the 
hotter parts of the temperate zone. 

The economical uses of the order are highly 
important. Cotton, on which so much of British 
commerce depends, is obtained from several species 
of Gossypium, and is the downy hairs which are 
attached to and envelop the seeds. These hairs, 
originally of a cylindrical form, at maturity become 
collapsed into flat bands, and are much twisted. 
Much confusion exists in botanical works relative 
to the species of Gossypium, the varying character 
of the plants having, it is feared, given rise to 
unnecessary names. The researches of Royle 
seem to indicate that all the forms known in com- 
merce should be reduced to four species of plants 
— namely, i. Gossypium herbaceum, which is the 
common cotton-plant in India, and a variety of 
which, with buff-coloured hairs, supplies the Nan- 
kin cotton. 2. G. arboreum, the tree-cotton of 
India, with red flowers and a fine silky cotton. 
3. G. Barbadense, Barbadoes cotton, called in 
India Bourbon cotton, which supplies the highly- 
esteemed Sea Island cotton, as well as the Georgia 
and New Orleans cottons. 4- G. Peruvianum, 
Cavanilles (or G. acuminatum), which supplies the 
Pemambuco or Brazil cotton. The great difference 
in the value of different kinds of cotton depends 
chiefly upon the length of staple, precise measure- 
ments of which have recently been published by 
the United States government. 

The inner bark of Hibiscus cannabinus furnishes 
a kind of sun-hemp in India- H. mutabilis has 

^ 91 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



showy flowers which change colour, passing in the 
•course of the day from a cream-coloured rose to 
■a. delicate pink or rich rose. H. tiliaceus yields 
Cuba-bast. The tree-mallow {Lavatera arhorea) 
^ows on rocks exposed to the influence of the sea, 
as on the Bass Rock and Ailsa Craig. Various 
■species of Sida furnish fibre. S. Phyltanthos and 
■S. Pichinchensis ascend, on the mountain of Anti- 
sana and the volcano Rucu-Pinchincha, to the 
•elevation of 13,000 or 15,000 feet. 

Many of the Malvaceae are also medicinal and 
dietetic. The pdte de Guitnauve, which is made 
from a species of marsh-mallow, is used on the 
continent in disorders of the lungs ; from the 
Althcea officinalis is prepared, in France, the vege- 
table tracing-paper known by the name of papier 
digital; and a blue matter, not inferior to indigo, 
is obtained from the leaves of the hollyhock 
{A. rosea). The Chinese blacken their eyebrows 
with the flowers of Hibiscus Rosa-sinensis, and 
Europeans apply it to the less honourable purpose 
of blacking their shoes. 

TERNSTRoMiACEiE. — This is one of the most 
interesting natural orders, as, besides other fine 
plants, it contains the cameUias and tea-trees. All 
the members are trees or shrubs, with very hand- 
some flowers. The leaves are alternate, and with- 
out stipules ; they are frequently leathery, and are 
sometimes marked with pellucid dots. The flowers 
liave generally five sepals and five petals ; some- 
times there are two additional sepals a little below 
the others. The stamens are numerous, and either 
^ow together into a central column, or are in five 
distinct bundles. There are but few seeds, which 
are large, and entirely filled with an embryo 
having thick cotyledons like the bean, and no 
albumen. 

Only a very few genera belonging to this order 
have been introduced into this country ; but there 
are a number of equally beautiful species found in 
the East Indies and South America. Those best 
Icnown in Britain are the genera Gordonia, Stuartia, 
Camellia, and Then. The common camellia — C. 
yaponica — is too well known to need any descrip- 
tion, and its beautiful flowers and thick glossy 
leaves must be familiar to every one. The double 
varieties are numerous, but the ' old double white,' 
as it is called, is still the favourite kind for ball- 
room decoration. The tea-tree is very nearly 
allied to the camellia, but its flowers and leaves 
are smaller. The teas of commerce are obtained 
from two different plants, named respectively Thea 
Bohea and Thea viridis, on the supposition that 
the former produced our ordinary black teas, while 
the latter afforded green tea. However, both 
kinds of tea are manufactured from either plant, 
the diffierence mainly depending on the time of 
gathering and the mode of preparation. The young 
leaves, quickly dried and subjected to a particular 
kind of manipulation, form green tea ; while the 
older ones, dried more slowly, and undergoing 
fermentation, constitute black tea ; but in some 
cases the green colour is imparted by means of a 
mixture of turmeric, Prussian-blue, and gypsum. 

Long confined to China, this branch of Oriental 
agriculture has at length been successfully intro- 
duced into India. The Assam Tea is furnished by 
a larger plant than either of the preceding, which 
is now regarded as a distinct species, T. Assamica. 

AurantiacEjE. — The golden fruit of the orange 
and lemon, so characteristic of this order, is so 

92 



beautiful, that it is supposed to have been typified 
by the celebrated apples of the Hesperides. The 
order consists of elegant and fragrant trees or 
shrubs. The leaves, though apparently simple, 
are compound, because they are articulated with 
the petiole, which in the orange and some other 




Lemon. 



species is winged. The calyx is tubular, with five 
short teeth. The petals of the corolla are five in 
number, thick and fleshy, and when held up to 
the light, they appear full of pellucid dots, which 
are receptacles of secretion filled with fragrant oiL 
There are generally twenty stamens, which are 
divided into five bundles, the filaments in each 
bundle adhering together. The fruit — hesperi- 
dium, as it is called by botanists — is divided into 
numerous cells by dissepiments, and there is a 
central placenta, to which the ovules are attached 
in the ovary ; but as the fruit swells, the seeds 
become detached, and the cells fill gradually with 
cellular tissue, till at last they become replete with 
an acid and bitter pulp, in which the seeds are 
immersed. The seeds are exalbuminous, and 
sometimes contain more than one embryo. 

The most familiar genus is Citrus, the species 
of which are chiefly natives of the tropics — most 
of them being found in a wild state exclusively in 
the East Indies. The orange, however, appears 
to have an extraordinary facility of adapting itself 
to any country the climate of which is dry and 
sunny ; and thus have arisen the orange groves 
of St Michael and of Florida, besides those of 
Malta, and various parts of Europe and North 
Africa. All the kinds of orange, lemon, shad- 
dock, citron, &c. belong to the genus Citrus. C. 
Aurantium is the sweet orange, so generally 
cultivated. The principal kinds are the common 
orange, the Chinese or Mandarin, the Maltese, 
and the St Michael. C. ntedica is the citron ; C. 
Limonum, the lemon ; C. Limetta, the sweet 
lime ; and var. Bergamia, the bergamot ; C. 
Paradisi, the forbidden fruit ; and C. decumana, 
the shaddock. The Wampee, the fruit of Cookia 
punctata, is much admired in China and the 
Indian Archipelago. ASgle Marmelos, the Indian 
Bael or Bela, yields a delicious fruit. 

All the Aurantiaceae aboimd in a fragrant oily 
matter, which is contained in the receptacles of 
secretion in the rind of the fruit, and in the leaves 



SYSTEMATIC BOTANY. 



of the tree. The pulp of the fruit is more or less 
acid. About 35,000 tons of oranges are said to be 
annually imported into Great Britain. The pro- 
ductiveness of the common orange is enormous : 
a single tree at St Michael has been known to 
produce 20,000 oranges fit for packing, exclusive 
of the damaged fruit and the waste, which may 
be calculated at one-fifth more. 

SapindacejE. — The Soapworts are woody, 
rarely herbaceous plants, with usually compound 
leaves and unsymmetrical flowers, most of them 
being found in the hot parts of India and America, 
and little known in Europe, except from the 
writings of travellers. This remark will not apply, 
however, to the HippocastanecSf or horse-chestnuts 
(distinguished by their opposite leaves, and by the 
ovary having two ovules — one erect, the other 
suspended — in each cell), which are natives of 
Northern India, Persia, and the American States. 
This section consists of only two genera — namely, 
^sculus, the horse-chestnut ; and Pavia, the 
scarlet-flowering chestnut The leaves are palmate 




iEsculus Hippocastanum. 

—that is, divided into five or seven parts ; and are 
without stipules. The flowers are produced in large 
panicles or racemose cymes. There are five petals, 
two of which are smaller than the others, and all 
have small claws. In the Pavia there are only 
four petals, two of which are so much smaller than 
the others as to look like leafy stamens. There 
are seven stamens, three of which are much 
shorter than the others. The fruit of the horse- 
chestnut consists of a leathery capsule, which 
opens when it is ripe into three valves. The 
capsule of Pavia is smooth. The scar of the hilum 
is very strongly marked on the testa of the nuts of 
both genera; and in Pavia it is so conspicuous 
as to give rise to the American name of the genus, 
which is called Buck's-eye, from the resemblance 
of the hilum to the pupil of an eye. The horse- 
chestnuts have been so long cultivated in Europe 
as now to spring up like natives of the soil. Both 
of the genera are amongst the finest of our flower- 
ing-trees, and on this account are common in 
park-scenery. The seeds of the order abound in 
starchy and in saponaceous matter. The bark 
of the common jEscuIus Hippocastanum is bitter, 
astringent, and has been recommended as a valu- 
able febrifuge in intermittent and other fevers. 
The Akee fruit {Blighia sapidd) ; the Li-chi 
{Nephelium Litchi) and Longan (A''. Longan)^ 



fruits of China; the Guarani plant {Paullinia 
sorbilts) of India, and the soap-berrj' {Sapindus 
saponaria), all belong to the order. 

ViTACEiE. — This order comprises about 260 
species, natives of temperate climates. Their pre- 
vailing habit is a long dangling growth of stem, 
with tendrils opposite the leaves, thyrsus of colour- 
less flowers, and bunches of berried fruit The 
stem and branches are furnished with tumid 
articulated nodes ; the leaves are lobed or com- 
pound, generally alternate with stipules. The 
flowers are small, often the male and female dis- 
tmct; calyx, very small; sepals and petals, four 
or five, the latter sometimes cohering at the tips, 
and falling off" before the bursting of the anthers ; 
stamens, equal in number to the petals, and 
opposite to them; ovary, two-celled; fruit, a 
berry, with the seeds immersed in pulp ; seeds 
with a bony testa ; albumen, hard ; embryo,, 
small The curious formation of the flower and 
berry is well illustrated by the dissection of the 
common vine, as shewn in page 88. 

The genera are — Ampelopsis, the vine-leafed 
ivy ; Vitis, the grape-vine ; Leea, Cissus, Pterisan- 
thes, and Rhaganus. With the exception of the 
vine, the other genera are of little interest, being 
employed only as ornamental creepers. The 
grape-vine is said to be a native of the shores 
of the Caspian, whence it has been widely dis- 
tributed, and greatly improved by cultivation. 

The properties of the fruit, either in its fresh 
state or dried to form raisins, or expressed and 
fermented to form wine, &c. are too well known ta 
require description. The average import of raisins 
to Britain amounts to more than 12,000 tons, the 
finest being the Muscatel The dried currants of 
commerce — a corruption of Corinths — are the pro- 
duce of the small seedless Corinthian grape, which 
is cultivated in many islands of the Mediter- 
ranean. Currants are annually imported to the 
extent of 21,000 tons. Vitis vulpina is a kind of 
wild vine which produces what are called fox-grapes 
in North America; it forms an ornamental creeper, 
being hardy in Britain ; and has recently attracted 
notice as likely to form a good stock on which to 
graft our grape-vines. The Kangaroo Vine of 
Australia, which is well suited as an indoor win- 
dow-creeper, is a species of Cissus, The berries 
of the Virginian creeper {A. Jiederacea) are small 
and unpalatable, but might be eaten with perfect 
safety. According to Von Martius, the leaves and 
fruit of C. tinctoria abound in g^een colouring- 
matter, which soon becomes blue, and is highly 
esteemed by the natives of Brazil as a dye for 
cotton fabrics. Acid leaves, and a fruit hke that 
of the common gi"ape, are the usual characters 
of the order. 

GERANlACEiE. — The Geraniacece comprise about 
500 species. They are herbs or shrubs, with 
stems which are tumid and articulated at the 
joints. The leaves are generally lobed, and fur- 
nished with small stipules. Calyx persistent in 
five-ribbed sepals, sometimes spurred. Corolla 
generally of five petals, with strongly marked 
veins. Stamens twice as many as the petals ; 
filaments slightly united at the base. Fruit con- 
sists of five elastic one-seeded carpels, adhering to- 
an elongated central axis, from which they curve 
upwards, by means of the elastic styles, when 
ripe. Seed without albumen ; cotyledons rolled 
up or folded. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



The chief genera are Geranium, Pelargonium, 
and Erodium, respectively crane's-bill, stork's-bill, 
and heron's-bill, from the fancied resemblance 
of the ripe seed-vessel to these objects. Many 
of the species, which are very widely distributed, 
are natives of Europe ; but the majority of our 
green-house favourites are from the Cape of Good 
Hope. The herb Robert {G. Robertianum) and 
the meadow crane's-bill {G. pratense) are British 
plants, as are also Erodium cicutarium and mos- 
chatum. All the pelargoniums have their flowers 
in heads or umbels, and the calyx remains till the 
seeds are ripe. Their leaves vary very much, 
some being round— as the horseshoe geranium — 
and marked with a dark line ; and others are 
deeply lobed, as some of the scented varieties. 

The Geraniaceae are all innocuous plants, being 
generally slightly acid, and sometimes astringent. 
They are all more or less fragrant, secreting oils 
and resins ; and in some these secretions are so 
abundant {Monsonia spinosd) that the stems burn 
like torches, and emit an agreeable odour during 
combustion. In America, the roots of G. macu- 
latum are used as a remedy for diarrhoea ; the 
British Erodiums are sometimes employed as 
aromatic bitters ; from P. odoratissimum a fra- 
grant oil has been distilled, resembling the attar 
of roses ; the underground tubercles of P. hirsu- 
tum are esculent, and prized by the Arabs as food ; 
the tubers of G. parvijlorum are eaten by the 
natives of Tasmania, where it is called the Native 
Carrot The pelargoniums, generally called gera- 
niums, which are seen at horticultural exhibitions 
are chiefly hybrids and improved varieties of the 
Cape species of Pelargonium. 

LinacEjE. — A small order. The flowers are in 
five parts, like those of the cloveworts ; but the 
sepals of the calyx are always distinct, and, instead 
of being arranged in a regular whorl, two are 
placed a little lower than the others, as in the 
Cistaces. There are five styles and stigmas ; but 
the seed-vessel splits into ten valves, each carpel 
containing two seeds, separated by an obscure 
partition, which gives the carpels the appearance 
of being only one-seeded. The seeds are flat and 
shining, with a large embryo. 

The only genera are Linum, Cliococca, and 
Radiola; the former comprehending many species. 
L. catharticum is the purging-flax of rural prac- 
tice. But of all plants of the order, the common 
flax {L. usitatissimum) is the most important and 
best known. Flax will grow in almost any part 
of the world ; and though an annual, its stem 
contains so much woody fibre that it is exceed- 
ingly tough and durable, yielding by maceration 
the flax of commerce. The seeds contain a 
great quantity of oil {linseed-oil), which is ob- 
tained from them by pressure, and the refuse 
forms oil-cake, employed by farmers in feeding 
cattle. The seeds also abound in mucilagin- 
ous matter, and are thus made use of medi- 
cinally, for coughs, &c. ; or, when ground into 
meal, for poultices. Though lint was at one time 
pretty extensively grown in Britain, our manu- 
facturers now derive the greater part of their 
supplies from the countries adjoining the Baltic, 
from which, in one year, not less than 70,000 tons 
of flax, and about 2,000,000 bushels of linseed, 
have laeen imported. The Valley of the Nile, 
anciently celebrated for its fine linen, now yields 
but an inconsiderable quantity, in consequence 

94 



of the present barbarous condition of the inhab 
itants. It is there cultivated during the cold 
season. Of late years, the fibres of flax, by being 
steeped in a solution of carbonate of soda, and 
afterwards dipped in a weak acid solution, are so 
broken up as to form a substance like cotton, 
which is manufactured in the same way as that 
fabric, 

§ CALYCIFLOR^ 

The plants comprised in this sub-class are di- 
chlamydeous — that is, having both calyx and co- 
rolla — as in the preceding ; the petals are usually 
separate, but sometimes united ; the stamens per- 
igynous, arising from the calyx, and thus sur- 
rounding the ovary ; or epig^nous, arising, appar- 
ently, from the upper part of the ovary, which is 
in this case inferior as regards the parts of the 
flower. It has been separated into two divisions : 
the one named Polypetalce, from the petals being 
several and separated ; the other Monopetalce, 
from their being so united as to appear single ; 
for example, a wild rose has five distinct petals, 
separate to the base, whereas a bell-flower (Cam- 
panula) has all its petals united into one piece. 
In no case do the stamens arise directly from the 
thalamus, which is the characteristic of the pre- 
ceding sub-class. Here the parts of the flower 
are more or less united to each other. The 
following are the orders belonging to Calyciflorse : 

POLYPETALiE. 



s 



Stackhousiaceae — Stackhou- 
siads. 
*Celastrace£e — Spindle-trees. 
*Staphyleaceae — Bladder-nuts. 

* Rhamnaceae— Buckthorns. 
Anacardiaceae— Cashews. 
Amyridaceae — Myrrh order. 
Connaraceae — Connarads. 

*Leguminosae or Fabaceae— Le- 
guminous Plants. 

Moringaceae— Moringas. 
"Rosacese — Rose order. 

Calycanthaceae^Calycanths. 

* Ly thraceas — Loosestrifes. 
Rhizophoracese — Mangroves. 
Vochysiaceae — Vochysia order. 
Combretaceae — Myrobalans. 
Melastomaceae — Melastomads. 
Alangiaceae — Alangiads. 
Philadelphaceae — Syringas. 
Myrtaceae — Myrtles. 
Chamaelauciaceae — Fringe- 
myrtles. 

Lecythidaceae — Monkey-pots. 

Barringtoniaceae — Barringto- 

nias. 



•Onagraceae - 
roses. 



•Halorageaceae — Mare's- tails. 

Loasaceae — Chili-nettles. 
•Cucurbitaceae — Cucumber or- 
der. 

Papayaceae — Papa w- worts. 

Belvisiaceae — Belvisiads. 

Passifloraceae — Passion-flowers. 

Turneraceae — Turnera order. 
*Portulacaceae — Purslanes. 

lUecebraceae — Knotworts. 
"Crassulaceae — Stonecrops. 

Mesembryanthemaceae — Fig- 
marigolds. 

Tetragoniaceae — Tetragonias. 

Cactaceae — Cactuses. 
*Grossulariaceae— Gooseberry or- 
der. 

Escalloniaceae — Escalloniads. 
•Saxifragaceae — Saxifrages. 

Hydra^ngeaceae— Hydrangeads. 

Cunoniaceae — Cunoniads. 

Bruniaceae — Bruniads. 

Hamanielidaceae — Witch-hazels. 
•Umbelliferae or Apiaceae — Um- 
bel-bearers. 
*Araliaceae — Ivyworts. 



■Evening Prim- *Cornaceae — Cornels. 



MONOPETAL.(E. 



*Loranthaceae — Mistleto order. 

' Caprifoliaceae — HoneysuckIe.s. 

*Rubiaceae — Cinchona and Bed- 
straw order. 

*Valerianaceae — ^Valerians. 

*Dipsaceae — Teazelworts. 
Calyceraceae — Calycera order. 

*Corapositae or Asteraceae — 
Composites. 



Brunoniaceae — Brunoniads. 

Goodeniaceae — Goodeniads. 

Stylidiaceae — Styleworts. 
*Campanulaceae — Bell-flowers. 
*LobeliaceaE — Lobeliads. 

Styracaceae — Storax order. 

Columelliaceae — Columellia or- 
der. 
*Vacciniaceae— Cranberries. 



LEGUMlNOSiE. — This is one of the most exten- 
sive and best defined orders in the vegetable king- 
dom. Many of its plants bear butterfly-shaped 
(papilionaceous) flowers, and all have pod-like 
seed-vessels ; among which may be mentioned, as 
familiar examples, the pea, bean, lupine, broom, 
furze, and laburnum. The following may be stated 



SYSTEMATIC BOTANY. 




Papilionaceous 
Flower. 



as the general characteristics of the Leguminosce : 
Herbs, shrubs, or trees ; leaves, alternate, generally 
compound, their petioles tumid 
at the base, where there are 
usually two stipules, and also 
two to each leaflet in the 
pinnate leaves ; the pedicles 
are generally articulated, and 
the flowers are furnished with 
small bracts ; calyx, five-parted, 
the segments being sometimes 
unequal and variously com- 
bined ; petals, never more than 
five, but often less, and some- 
times wanting, inserted into the base of the calyx, 
and variously arranged, papilionaceous in all 
European genera, the odd petal being always 
superior ; stamens, definite or indefinite, inserted 
with the petals, in exceptional cases apparently 
hypogynous, thus shewing a transition from the 
preceding sub-class, distinct, or in one, two, or 
three bundles ; ovary, superior, for the most part 
one-celled ; ovules, one or many ; style and 
stigma, simple ; fruit, a true legume, a modified 
form of legume or loment, or sometimes, when 
containing only one seed, drupe-like ; embryo, 
straight, with or without albumen ; the radicle, 
in some instances, bent along the edge of the 
cotyledons. 

The plants belonging to the order are found in 
all parts of the world, but they are most abundant 
in warm regions, and diminish on approaching 
the poles. There are above 6500 known species. 

This family is amongst the most important to 
man, whether as arfordirij objects of beauty, of 
utility, or of nutriment. The bean, the pea, the 
vetch, and the clover tribe belong to it ; as do 
the logwood, the laburnum, indigo, the tamarind, 
liquorice, senna, and the acacias. Its general pro- 
perties are considered by some to be wholesome, 
but there are several exceptions. Thus, the seeds 
of laburnum, and the juice of Coronilla varia, are 
poisonous. Senna, obtained from various species 
of cassia, is purgative, and several others of the 
order possess a similar property. The pericarp of 
some contains much tannin ; dyes are obtained 
from others ; and many yield gums and balsams. 
It would occupy pages to enumerate all the uses 
to which this, one of the most extensive orders in 
the vegetable kingdom, has been applied. We 
shall, therefore, briefly indicate the principal sec- 
tions of the order, and the more important plants 
contained in each. — § I. Papilionacece, petals pa- 
pilionaceous, imbricate, upper one exterior. This, 
which may be called the Pulse section, is the only 
one containing British species, but these are 
numerous, and contribute much to the beauty of 
our Flora. The vetches and lathyrus, the rest- 
harrow, the trefoils and clovers, the lotus and the 
meliloti, are all gay flowers which we gather in our 
rural walks. Turning to plants of utility, we find 
here the bean and the pea, the clovers, vetches, 
sainfoin, and lucerne. The lentil {Ervum lens), 
although a crop of the most ancient cultivation, has 
only recently been introduced to the notice of Brit- 
ish farmers; and may possibly be of some service 
on light soils. Kidney-beans and scarlet-runners 
also belong to the garden Papilionaceae, the latter 
affording a characteristic illustration of the mis- 
cellaneous properties of this order, its roots being 
poisonous, while its seeds form an article of food. 



Other plants of the section are decidedly poisonous, 
such as Coronilla varia, and the seeds and bark 
of laburnum, which, being a common ornamental 
tree, and one which seeds freely, is apt to give 
rise to accidents, especially in the case of children. 
But perhaps the most remarkable of all poisonous 
species is the ordeal bean of Calabar, Physostigma 
venenosum. It is commonly used in Calabar in 
trials by ordeal, the suspected party being set free 
if (by vomiting) the bean does not prove fatal In 
like manner, the bark of another species is used 
by the Caffres as a test in judicial trials. Of mis- 
cellaneous plants used in the arts, we find Astra- 
galus gummifer and other species, from which 
gum-tragacanth is obtained ; Baptisia tinctoria, a 
dye-plant and the wild indigo of America ; Crota- 
laria juncea, whose fibrous bark yields Bengal 
hemp; Dalbergia Sissoo, which in India yields 
the valuable timber well known by its native name 
of Sissoo ; Dipterix odorata, whose fragrant seeds 
are the Tonka-beans of commerce ; Glycyrrhiza 
glabra, whose root forms liquorice ; various species 
of Indigo/era, from which the true indigo is 
obtained ; Pterocarpus santalinus, the source of 
red sandal-wood ; P. draco, which yields gum- 
dragon ; and Triptolomea, from species of which 
the rose-wood of commerce appears to be derived. 
Kino is supplied by various species oi Pterocarpus, 
and by Butea frondosa, one of the most gorgeous 
plants of India, with masses of bright orange-red 
flowers, resembling sheets of flame. — § II, Casal- 
piniecB, petals imbricated, upper one interior. The 
plants of this section are chiefly important from 
yielding valuable timbers and dyes, while some 
are much used as purgative medicines. Of the 
latter, the various kinds of senna, consisting of the 
leaves of species of Cassia, are most important. 
The fruit of the tamarind likewise contains a laxa- 
tive pulp, as also Cassia Fistula. Of dyes we 
have the sappan of India {Casalpinia sappan), 
the barwood or camwood {Baphia nitida), and 
the well-known logwood {Hcematoxylon cantpech- 
ianuni). Of timber-trees, the Brazil-wood of com- 
merce {Ccesalpinia Brasiliensis) is not the least 
important. The West Indian locust-tree {Hymenaa 
Courbaril) affords a close-grained tough wood, 
which is found well adapted for the beams of 
steam-engines, while the Guiana purple-heart even 
excels it in toughness ; and being found to resist 
well the shock of artillery discharges, it is sought 
after for mortar-beds. — § III. Mimosece, petals 
valvate in estivation. The principal genera are 
Acacia and Mimosa; the latter genus chiefly 
remarkable on account of the irritabiUty displayed 
by the leaves of M. pudica and sensitiva. Many 
species of Acacia yield gum-arabic and gum-sene- 
gal. The Australian species, called ' Wattles,' have 
astringent bark which is used in tanning ; in these 
the leaf-stalk is often flattened into a phyllodium, 
or false-leaf ; in the young plant there may be no 
compound leaves developed, but these ultimately 
appear at the tips of the phyllodia. 

RosACEiE. — Like the preceding, this is one of 
the most extensive natural orders, comprehending 
nearly 1000 described species, which are herbs, 
shrubs, and trees, often of very dissimilar habits 
and appearance, but all bearing a striking resem- 
blance in their fructification to the single or wild 
rose of our woods and hedges, which may be taken 
as the type of the order. Among the trees may 
be mentioned, as familiar examples, the almond 

w 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




Rosaceous Flower. 



{Amygdalus), the pear and apple iPyrus), the 
sloe and plum {Prunus), the peach and nectarine 
{Perstca), the cherries 
and laurels (Cerasus) ; 
among the shrubs, the 
rose (Rosa), the hawthorn 
{CratcBgus), the bramble 
and raspberry {Rubus), 
and the quince (Cy^/iS'w/fl) ; 
among the herbs, the 
common yellow Poten- 
tilla of the roadsides, the 
Geum, the Tonnentilla of 
our woods and commons, and the delicious straw- 
berry {Fragarid). From the varied nature of its 
genera, the order is divided by some authors into 
seven sub-orders for the purposes of detailed 
description. All the different sections exhibit the 
following general characteristics : Leaves, alter- 
nate, generally compound, and always furnished 
with stipules ; calyx, five-lobed, united below, but 
separate and expanding above ; corolla, of five, 
or sometimes four petals. The ovary is one-celled, 
and there is seldom more than one seed, scarcely 
ever more than two in each cell. Carpels numer- 
ous, and generally inclosed in the fleshy tube of 
the calyx. 

The following are the sub-orders : i. Chryso- 
BALANEjE, or cocoa-plum family, represented by C. 
icaco, a shrub found in the West Indies, where its 
fruit, which is about the size of a plum, of a whitish- 
yellow, and possessing a sweetish taste, is brought 
to the markets. There are about nine genera be- 
longing to this tribe, all of which are trees or shrubs, 
with simple alternate stipulate leaves, and flowers 
in racemes or panicles. They are natives of the 
tropical countries, and differ from the almond tribe 
in having irregular petals and stamens, and in the 
style arising from the base of the ovary ; the 
stipules are not united to the petiole. — 2. Amyg- 
DALEiE, or almond family, represented by the 
common almond {Amygdalus co?nmunis), and 
embracing the peach, apricot, nectarine, plum, 
cherry, &c. well known for their delicious fruits, 
and a few bushes remarkable for their gay appear- 
ance during the flowering season. The fruits of 
this tribe are for the most part edible ; and though 
the leaves and bark possess medicinal properties, 
yet one of the most subtile poisons — prussic acid 
— can be extracted both from the fruit and leaves 
of the almond. — 3. RosEvE, or roses proper, the 
type of which is the single wild-roses of our hedges. 
The section is distinguished botanically by the 
numerous achenes inclosed in a fleshy calycine 
tube which is contracted at the orifice. They have 
all a corolla of five equal slightly indented petals, 
capable of being increased indefinitely by cultiva- 
tion ; numerous stamens ; a five-cleft calyx. The 
pitcher-shaped portion of the calyx becomes the 
hip as the seeds ripen, and forms a false 
pericarp, inclosing the numerous bony carpels. 
Many of the plants have pinnate leaves and 
prickles on their stems. Most of them are fra- 
grant, and the leaves of some, as the sweet-brier, 
are replete with a fragrant volatile oil, which 
appears to be secreted by glands dispersed all 
over the foliaceous surface of the plant. — 4. POTEN- 
TlLLlDiE, embracing those plants which agree 
with the common Potentilla in the construction of 
their flowers — that is, in having a calyx of ten 
sepals ; its tube short, or nearly flat, not inclosing 

96 



the fruit ; a corolla of five petals ; and the stamens, 
which are numerous, forming a ring round an 
elevated or flat receptacle, on which are placed 
numerous carpels. By this test the student will 
find that the section comprises not only herbs, 
such as the potentilla, geum, tormentilla, and 
strawberry, but also erect and trailing shrubs, as 
the raspberry and bramble. These genera, though 
alike in their flowers and in many of their habits, 
are otherwise very dissimilar. In the potentilla, 
for example, the carpels form the prominent part 
of the so-called fruit, while in the strawberry the 
receptacle becomes fleshy and edible. Again, in 
the raspberry, the receptacle is a torus surrounded 
by the carpels, which swell out and soften, forming 
the edible portion. The leaves and stems of these 
genera are also very dissimilar, but the habit of 
increasing by suckers or runners is prevalent in 
all. — 5. Sanguisorbid^, a section of herbaceous 
perennials, illustrated by Sanguisorba officinalis^ 
or the weed burnet of our pastures. This tribe is 
distinguished by having one or two achenes in- 
closed within the dry calyx-tube. The flowers 
often have no petals, but the clefts of the calyx arc 
coloured, and the flowers are generally furnished 
with glossy coloured bracts. — 6. Spir^eid^, decid- 
uous shrubs and perennial herbs, represented b\' 
Spircea Ulmaria, or meadow-sweet. In this sec- 
tion, the five-cleft calyx is lined with the dilated 
receptacle, which forms a sort of cup for the 
carpels, which are in the fonn of follicles. The 
beautiful hardy shrub named Neillia thyrsijlora 
belongs to this tribe, which contains a large number 
of shrubby ornamental Spirceas, as well as her- 
baceous kinds. — 7. PoMEiE, an extensive and 
varied section, the type of which is the common 
apple {Pyrus malus). It comprehends the apple, 
pear {Pyrus communis), the mountain-ash {P. 
aucuparid), the white beam-tree {P. Aria), the 
quince {Cydonia), and the hawthorn {CratcBgus). 
In all of these genera, which are trees and shrubs, 
the flowers are remarkably similar ; but the habits 
of the plants, the leaves, and the fruit, present 
numerous differences. 

The properties of the order have already been s» 
far noticed in the preceding detail, that it may be 
stated of them generally as follows : The fruit of 
some of the Chrysobalanece is eaten under the 
name of the cocoa-plum. The AmygdalecB include 
the almond, plum, cherrj', and sloe ; the leaves 
and kernels contain prussic acid, which, in a 
concentrated form, is one of the subtilest poisons ; 
but being generally diluted in a natural state with 
gum, sugar, &c. it is harmless, and serves to give 
an agreeable flavour to the fruits containing it. 
The RosecB are chiefly valued for their ornamental 
flowers, but they also yield valuable extracts — as 
attar of roses, rose-water, conserve of roses, &c. 
The fragrant essential oil called attar of roses is 
distilled chiefly from the common cabbage-rose 
{Rosa centifolid) and its varieties ; 20,000 flowers 
of roses are required to make a rupee weight of 
the attar, which sells for £,\o. The general char- 
acter of the SanguisorbidcE is astringency. The 
roots of Spircea filipe7idula and Ulmaria, as well 
as those of some other plants belonging to the 
SpircBidcB, have been used as a tonic. Of the 
Poteyiti Hides, the roots of several are astringent 
and febrifugal, and the fruits of such as the rasp- 
berry and strawberry are delicious and wholesome. 
The Pomea, under cultivation, supply wholesome 



'i 



SYSTEMATIC BOTANY. 



and delicious fruits, of which the apple, pear, 
quince, and service-berry are familiar examples. 

Myrtace.^. — The order consists of upwards of 
60 genera, and about 1300 known species. They 
are all trees or shrubs, with simple exstipulate 
leaves, which are for the most part opposite, full 
of transparent dots, and with an intra-marginal 
vein round the edge. The substance of the leaf is 
coriaceous, and the dots are glands, or cysts, full 
of a fragrant volatile oil The inflorescence is both 
terminal and axillary, variable in its form, but 
generally aggregate — the flowers being regular and 
united, of a white, red, or sometimes yellow colour, 
but never blue. The tube of the calyx adheres to 
the ovary, and is from four to eight cleft, persistent 
or deciduous. The petals, which are rarely want- 
ing, are equal in number to, and alternate with, 
the segments of the calyx ; the stamens are in- 
serted with the petals, and are twice as many, or 
(usually) indefinite, and then aixanged in several 




Pomegranate. 

series ; the anthers are two-celled, and burst longi- 
tudinally. Fruit, baccate or capsular ; style and 
stigma, simple ; many-celled, or one-celled by the 
obliteration of the dissepiments of the carpels. 
Seeds, generally indefinite, seldom few, and without 
albumen. 

Among the edible fruits belonging to the order 
may be mentioned the delicious guava, yielded by 
several species of Psidium; the rose-apple and 
jamrosade, produced by Eugenia and Jambosa. 
Of spices yielded by the order, which are all more 
or less aromatic, we have the clove, which is the 
unexpanded flower-bud of the Caryophyllus aro- 
maticus; all-spice, Pimento or Jamaica pepper, 
the dried berries of Eugenia pimento; and also 
the dried berries of the common myrtle. It is the 
volatile oil found in the dots of the leaves, the 
unexpanded petals, and in almost all the parts of 
the plant, that gives to them their fine aromatic 
fragrance. The pomegranate {Punica granatum) 
forms a delicious fruit in warm countries ; the 
pericarp or rind is used in the East as an astrin- 
gent ; and the bark of the root is esteemed an 
efficient anthelmintic. 

Some soecies of the beautiful genus Metrosideros 
yield hard and heavy timber, which the South Sea 
islanders prize for their clubs and other weapons 
of war. The gum-trees of Australia (^Eucalypti) 
deserve special notice as among the most valuable 
economical plants of our Australian colonies. They 
are distinguished by a remarkable operculate calyx, 



and their bark separates in layers, giving rise to 
the statement that the trees of Australia shed their 
bark instead of their leaves in winter. Their 
leaves often stand in a vertical position, and are 
remarkably hard and coriaceous. These trees 
grow to an enormous size, and yield very durable 
timber. They supply the place of the European 
oaks as a source of tannin. E. resinifera yields, 
on incision, an astringent matter, called Botany 
Bay kino; while several others yield saccharine 
matter. A peculiar red gum is contained in 
cavities of the wood of E. robusta. The leaves of 
some species oi Leptospermum are used in Australia 
as a substitute for tea. 

CucURBiTACEiE.— This is a large and interesting 
family of herbaceous plants, containing 56 known 
genera, and about 300 species. The roots are 
annual or perennial, fibrous or tuberous ; the stems 
succulent, climbing by means of lateral tendrils 
formed of the abortive stipules, and furnished with 
large alternate, palmated rough leaves. The flowers 
are usually unisexual. 

The Cucurbits are natives of all hot climates, 
but are most abundant in India and South America ; 
a few exist in the northern parts of Europe, and 
some are found at the Cape of Good Hope. In 
an economical point of view, the order is of con- 
siderable importance, furnishing the well-known 
esculents — the cucumber, melon, gourd, pumpkin, 
and calabash ; and the purgatives colocynth and 
elaterium. The general properties of the gourd 
family may be regarded as bitter and purgative — 
these qualities pervading more or less all the 
species, and rendering their fruit either esculent 
or purgative. The seeds of all are sweet and oily, 
and from some a considerable quantity of fine- 
flavoured oil may be expressed. The roots and 
leaves are sometimes replete with a bitter drastic 
juice. The fruit of many of the members g^rows to 
an enormous size ; the calabash, for example, being 
sometimes found six feet long and eighteen inches 
in circumference. Gherkins are the fruit of the 
common cucumber, pickled when in a young state. 
The fruit of Lagenaria vulgaris is in common use 
for water-bottles in the Greek islands and generally 
in the East. It has probably given rise to the 
clay water-bottles in form of a round bulb ending 
in a long neck, which much resemble it in shape, 
and to which the bottles in use all over the world 
may be traced as modifications. Many of the 
ornaments of ancient Egyptian architecture are 
traceable in a similar manner to vegetable forms 
peculiar to the region. 

Cactace^. — The Indian figs, or Cacti, consti- 
tute one of the most singular and interesting orders 
in the vegetable kingdom. They are unique in 
their forms and habits, having perennial succulent, 
angular, or rounded spiny stems. In general, the 
stems and branches are jointed; the leaves are 
either very minute, or altogether wanting, their 
place being supplied by strong spines. They are 
all natives of tropical America, but thrive well in 
all hot, dry, and exposed places. Of the more 
common genera, we may mention the following : 
Mammillaria, so called from the pap-like tubercles 
which cover its sub-cylindrical stem. Each tubercle 
is crowned with a little tuft of radiating spines ; 
and the flowers, which are sessile, are ranged in a 
kind of zone round the plant. The melon cactus 
{Melocactus communis), which has a more or less 
globose stem, with alternate furrows and ridges. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



the latter being armed with tufts of spines; the 
stem is crowned by a woolly tuft, from which 
spring the flowers. The hedgehog-thistle {Echtno- 
cactiis) has also a globose stem, but wants the 
woolly head, and has its flowers springing from the 
tufts of spines which arm the ridges. Some of 
the species grow to an enormous size. A plant of 
E. piatyceras, growing at Kew, measured 9 feet 
in height, 9^ in circumference, and weighed 
upwards of a ton. The torch-thistle {Cereus) has 
the stem angular, the projecting angles being armed 
with spiny tufts, from which the flowers generally 
spring. The old-man cactus {Polocereus senilis) is 
so called from its resemblance to an old man's 
head, being covered with long white hairs. The 
Peruvian torch-thistles {Cereus pemvianus and 
hexagonus) are still more gigantic plants, often 
attaining a height of forty feet, though their 
stems be not thicker than a man's arm. The 
rat's tail cereus (C. flagelliformis) is well known 
from its long whip-like stems, which hang down 
from the sides of the suspended pots in which 
it is usually grown. The night-flowering cereus 
(C grandtfiorus), so called from its blossoms 
opening during night, and fading before morning, 
has an angular, branched, and climbing stem, 
throwing out roots at every point. The genus 
Rhipsalis has slender jointed stems, which look 
like samphire ; and the opuntias, which are 
numerous and useful, are distinguished by their 
round, flat, leaf-like bodies, united together by 
joints, and for the most part covered with spines. 

The fruit of many of the Cactaceae is esculent, 
but is rather insipid, having little of that acidulous 
flavour which characterises the Currantworts, to 
which the family is allied. It is upon the Opuntia 
cocchinellifera, the Nopal plant, that the cochineal 
insect, so valuable in the arts, chiefly feeds. In 
the south of Europe, the prickly pear {0. com- 
munis) is reared as a hedge, and also for its fruit, 
which is edible, and yields a rich carmine pig- 
ment ; and the Indian fig {O. tuna) is grown for 
similar purposes in Brazil. 

GROSSULARlACEiE. — This is a well-known order, 
consisting principally of one genus, Ribes, which 
includes all the gooseberries and currants of our 
gardens. The species, of which there are upwards 
of eighty, are unarmed or thorny shrubs, with 
round or irregularly angled stems and branches ; 
simple, lobed, alternate leaves, destitute of stipules 
and tendrils. The inflorescence is axillary and in 
racemes. The calyx, which is often coloured, is 
four or five cleft ; petals, perigynous, equal in 
number to, and alternate with, the segments of the 
calyx ; stamens, of the same number, alternate, 
and inserted with the petals ; filaments, distinct ; 
anthers, two-celled, bursting longitudinally ; ovary, 
one-celled, cohering with the tube of the calyx ; 
ovules, indefinite ; fruit, a berry, crowned with the 
remains of the flower, one-celled, filled with pulp 
with two parietal placentas ; seeds, numerous, sus- 
pended among the pulp by filiform funicles ; testa, 
externally gelatinous ; albumen, horny. 

The order is very conveniently grouped into two 
sections — namely, the Gooseberries, which have 
prickly stems, and the flowers either singly, or in 
clusters of not more than two or three ; and the 
Currants, which are entirely without spines, and 
the flowers in racemes. There are a few species, 
such as Ribes dracantha and saxatile, which may 
be considered as intermediate, these having the 

98 



spines and habit of growth of the one, and the 
racemose inflorescence of the other. The common 
gooseberry {R. Grossularia), the red currant {R. 
rubrum), the black currant {R. nigrimi), and the 
flowering currant {R. sanguifieufn), are familiar 
examples of the order, and all too well known to 
require any detailed description. The gooseberry 
is found wild in many parts of Britain ; and is 
reared in the north of England to greater perfection 
than in any other country. 

Gooseberries and currants have agreeable acid 
fruits, the acidity or sweetness depending upon the 
relative quantities of malic acid and sugar which 
they contain. The blackberry has tonic and 
astringent properties, infusions of the leaves being 
used for this purpose. 

Saxifragace^. — This order consists chiefly of 
very small herbaceous plants, with alternate or 
opposite leaves, and is readily distinguished by 
the peculiar ovary, which is more or less com- 
pletely inferior, consisting of two carpels which 
diverge at the apex. As useful plants, they are 
unimportant, but they are the most charming that 
greet the eye of the botanist in his mountain 
rambles. Saxifraga stellaris and S. aizoides are 
the great ornaments of Highland streams at a low 
elevation ; while higher up, the rocky banks are 
covered with a purple carpet of S. oppositifolia, or 
the rarer S. rivularis, which attracts many a 
botanist to the summit of Loch-na-gar. S. cer7iua 
is confined to the summit of Ben Lawers. But it is 
not alone the Scottish mountains that are adorned 
with these 'alpine gems ;' S. Boussingaultii reaches 
to nearly 16,000 feet on Chimborazo. 

UMBELLlFERiE. — This is one of the most exten- 
sive and important of the natural orders, compris- 
ing about 300 genera, and above 1500 species. 




Common Hemlock : 
c, flower ; d, seed. 

The genera, though presenting many minor differ- 
ences, are, on the whole, well marked ; so that no 
one who has seen the flower of the parsley and 
common hemlock can have any difficulty in 
detecting an umbelliferous plant. The species are 
for the most part herbs, seldom shrubs, with 
fistular furrowed stems, loving damp waste places, 
and varying much in their properties, according 
to the climate under which they are grown. The 
leaves are generally divided, sometimes simple ; 
are alternate, and clasp the stem by a broad 
sheathing petiole. The flowers are white, pink, 



SYSTEMATIC BOTANY. 



yellow, and blue, and in umbels, which are simple 
or compound, and these are with or without bracts 
at their base : when seated at the base of the 
umbel, the bract is called an involucre ; when at 
the base of the umbellules in the compound head, 
an involucel. The calyx is superior and five- 
toothed ; petals, five, and inserted on the outside 
of a fleshy disc, which is placed on the top of the 
ovary ; stamens, five, and inserted alternately with 
the petals ; ovary, inferior, and two-celled, with 
pendulous ovules ; styles, two, distinct ; stigmas, 
simple. The fruit (cremocarp) consists of two 
carpels, united by a common axis, from which they 
separate when ripe ; the external part of the 
carpels is traversed by linear ridges, which are 
divided into primary and secondary, there being 
five of the latter, and four of the former, between 
them. The ridges are separated by channels, 
below which are often placed, in the covering of 
the seed, receptacles or vittas of an oily matter. 
The seed is pendulous, usually cohering with the 
carpel, rarely loose. 

Among the more familiar genera may be men- 
tioned the parsnip {Pastinaca), the cow-parsnip 
(.Heracleuni), the celery {Apium), the carrot 
(Dauats), the hemlock {Conium), the cow-bane 
{Ctcuta), and the coriander {Coriandruni). 

The properties of the order are very various. 
Some of the plants are harmless and esculent, 
while others are narcotic poisons ; a third set are 
antispasmodic, owing to the presence of a gum- 
resin containing a fetid sulphur oil ; while a fourth 
set are carminative, from containing a volatile oil. 
I. Among the harmless plants used as esculents 
may be mentioned the chervil, celery, arracacha, 
earth-nut, pig-nut, samphire, carrot, fennel, parsnip, 
parsley, and skirret 2. Poisonous plants contain- 
ing acrid and narcotic principles : fool's parsley, 
water hemlock or cow-bane, spotted hemlock, and 
hemlock-dropwort or dead-tongue. The last-named 
plant has been found to be poisonous only in 
certain localities. 3. Gum-resinous species, usually 
with a fetid odour : Narihex assafoetida, a native 
of Persia, yields the true assafoetida ; Ferula 
orientalis furnishes a fetid resin in Morocco ; 
Galbanum officinale and Opoidia galbanifera yield 
galbanum ; Dorema ammoniacum yields the Per- 
sian gum ammoniac ; Opoponax chiromtm pro- 
duces the gum-resin called opoponax. 4. Aromatic 
and carminative plants, containing volatile oil : 
caraway, dill, coriander, cummin, carrot, anise, &c. 

CaprifoliacE/E. — A well-known order, consist- 
ing of 12 or 14 genera, and about 220 species. 
They are erect or twining shrubs, rarely trees, 
having opposite, simple, or pinnate leaves, without 
stipules ; and flowers terminal in corymbs, or 
axillary. The flowers are white, scarlet, or yellow, 
and often sweet-scented, as in the common honey- 
suckle. The order has been divided into two 
sections — namely, the SAMBUCEiE, or elder tribe, 
and the Lonicer-iE, or true honeysuckle tribe, 

RUBiACEiE. — This is a large, and in many 
respects not a well-defined order, composed of 
small trees, shrubs, and herbs. It has been divided 
into two orders by some authors : CiNCHONACEyE, 
containing those plants most resembling cinchona ; 
and GALlACEiE, or SxELLAXiE, those most resem- 
bling the galiums or bedstraws. The Cinchonacece 
and Galiacece, indeed, form two well-marked groups 
of plants, abundantly distinct from each other in 
habit and in geographical distribution : the one 



consisting of trees, shrubs, and herbs, with simple 
opposite leaves and interpetiolar glandular stipules ; 
almost exclusively inhabiting the hotter parts of 
the world, most of them eminently conspicuous 
for their economical products and the beauty of 
their broad foliage and flowers ; the other com- 
posed entirely of straggling herbaceous plants, 
with weak angular stems and narrow verticillate 
exstipulate leaves, inhabiting northern countries, 
and, with one or two exceptions, alike inconspicu- 
ous for use and ornament Unfortunately, how- 
ever, fructification does not supply any character 
whereby those two ideally distinct groups of plants 
can be clearly separated from each other, and in 
the limitation of natural orders something more 
than a difference of habit is considered requisite. 
The recent discovery of the peculiar axillary glands 
of Cinchonacece in Galiacece serves still further to 
break up the supposed distinctions between these 
groups. De CandoUe has proposed a further sub- 
division into thirteen sub-tribes. 

By far the greater number of the species are 
tropical plants, though many are amongst the 
most common and neglected of British weeds. 
Madder {Rubia tinctorum) is common in gardens, 
and is much cultivated in Belgium and Holland 
for its roots, which yield a rich brownish-red dye, 
called Turkey red. The Galiums or bedstraws are 
familiar plants, growing on hedges, on dry banks, 
or sides of old ditches, and known by the common 
name of cleavers, ladies' bedstraw, crosswort, and 
the like. Asperula odorata, another of the order, 
is the well-known woodruff', which acquires, when 
dried, a most delicate fragrance. The coffee-tree 
{Coffea), Jesuit's bark {Cinchona), the Cape jasmine 
{Gardenia), and ipecacuanha {Cephdelis), are also 
well-known members. 

The properties of the order are very varied. 
The roots of many, as the madders and bedstraws, 
contain a large quantity of colouring matter ; and 
it is said that fowls fed upon the roots of some 
plants of this order have their bones dyed of a 
red colour ; in other cases, the plants are acrid, 
emetic, purgative, or diuretic. The bark (as that 
of the Cinchona, or Peruvian bark) is sometimes 
bitter, tonic, and astringent. The ipecacuanha 
plant {Cephdelis ipecacuanha) of South America, 
the annulated root of which is so valuable in 
medicine, and by which it is easily propagated, 
has been lately (1871) introduced into India by 
the government, for the purpose of cultivation. 
Many of the plants were grown and sent out from 
the Royal Botanic Garden of Edinburgh. Quinine, 
now so extensively used in medicine, is obtained 
from different species of cinchona, but chiefly from 
the bark and young shoots of C. Calisaya. The 
cultivation of cinchona is now being successfully 
carried on in India, and it has been lately intro- 
duced, with that object, into Java and Australia. 
The value of the roasted albumen of the coffee- 
berry is too well known to require allusion ; and 
the fruits of others of the order have been recom- 
mended as answering the same purpose. 

COMPOSlTiE, — This is one of the most extensive 
of the natural orders, containing not fewer than 
900 genera, and between 9000 and 10,000 species. 
The members are herbaceous plants or shrubs, 
with leaves alternate or opposite, without stipules, 
and usually simple. What is called the flower is 
an aggregation of unisexual or hermaphrodite 
florets, collected in dense heads upon a common 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



receptacle, surrounded by an involucre, as exem- 
plified in the common daisy and dandelion* As 
the compound leaf is composed of a number of 
leaflets, so is the composite flower made up of a 
number of florets arranged on one receptacle, 
which is furnished with a calyx-like involucre. 
Each floret is complete in itself, having all the 
appendages of bracts, calyx, corolla, stamens, and 
pistil, although the calyx is in a much reduced 
state, appearing in the form of bristly hairs. The 
corolla is monopetalous, and either ligulate, tubular, 
or bilabiate — that is, has two equal lips cut into 
several lobes. The stamens are equal in number 
to the teeth of the corolla, and alternate with 
them ; the anthers grow together, so as to form a 
kind of cylinder, through which passes the style, 
ending in a two-lobed stigma. The ovary is 
inferior, one-celled, with a single erect ovule. The 
fruit is an achene, which retains the pappus when 
ripe, and falls without opening ; the appearance 
of this pappus or down is familiarly illustrated in 
the head of the ripe dandelion. 

The order has been divided into three sections : 
I. Cichoracea, in which all the florets are ligulate 
and perfect. 2. Corymbifera, most of the florets 
tubular, all hermaphrodite, or those of the cir- 
cumference filiform or tubular, and pistihferous or 
ligulate ; style, not jointed. 3. Cynarocephalce, all 
the florets tubular ; style, jointed. The Composite 
plants are widely scattered over the globe, forming, 
according to some authorities, one-twelfth of its 
vegetable productions. Humboldt states that they 
constitute one-seventh of the flowering-plants of 
France, one-eighth of those of Germany, one- 
fifteenth of those of Lapland, a sixteenth of those 
of New Holland, a sixth of the North American 
Flora, and one-half of that of America within the 
tropics. The Composites are herbaceous in the 
colder quarters of the globe, and become shrubby 
as we approach the equator. 

The Cichoraceas are well illustrated by the 
common lettuce {Laciuca), the dandelion {Taraxa- 
cu)n), the succory {Cichoriufn), and the sow-thistle 
(Sonchus), which are common British plants. All 
the members of this section yield a milky juice, 
which is bitter, astringent, and slightly narcotic. 
Many of them are used in medicine — as the lettuce, 
from which the narcotic and diuretic Lactucariuni 
is obtained. Many are also used as articles of 
food ; thus, endive {Cichorium Endivid) is em- 
ployed as a salad ; so is the garden lettuce when 
young, the root of the sonchus, and perhaps, more 
than all, the root of C. Jntybus, or wild succory, 
which is roasted and largely mingled with coffee 
under the name of chicory. The Corymbiferae, 
which have the central florets tubular, and the 
outer ones generally ligulate, are illustrated by the 
daisy {Bellis perennis), the chamomile (fig.) {An- 
themis nobilis), the groundsel {Senecio), the tansy 
{Tanacetum vulgare), dahlia, marigold, &c. The 
juice of this section is watery; sometimes bitter 
and tonic, and sometimes acrid. Many of them 
contain volatile oils, which are used for various 
purposes, and some yield yellow and other dyes. 
Among the most useful of the section may be men- 
tioned the Jerusalem artichoke, wormwood, cham- 
omile, tansy, and arnica — the last much employed 
in homoeopathic practice ; indeed, most of the 
Corymbiferje are of medicinal value. Cynaro- 
cephalce. — The plants of this division are bitter and 
tonic. By cultivation, this bitterness is lessened, 
100 



and they become edible. The section may be 
illustrated by the cardoon and common artichoke, 




Chamomile. 

all the thistles {Carduus), the burdock {Arctium)^ 
the bluebottles {Centaiirea), the safflower {Caj-tha- 
vius). The properties of the artichoke are well 
known, as are also those of the carthamus, which 
is used in dyeing as well as in medicine. The 
thistle is chiefly interesting as being emblematical 
of Scotland ; but neither antiquaries nor botanists 
have been able to discover with certainty the 
species entitled to the appellation of the Scotch 
thistle. Onopordum Acanthmin adorns the grave 
of Burns in Dumfries, and is usually employed in 
national demonstrations ; but Burns had another 
species in view as the ' bur-thistle ' — namely, Car- 
duus lanceolatus. Others prefer the milk-thistle ; 
and so far as the figures on the coins of the Scotch 
kings indicate a special species, the milk-thistle 
appears to be the one indicated. 

§ COROLLIFLORiE. 

In this section the flowers are dichlamydeous, 
the petals united into a tube, hypogynous, stamens 
inserted in the corolla (or in the first four orders 
arising directly from the receptacle). The plants 
may usually be recognised by the corolla appearing 
to consist of one piece, the petals being united 
(gamopetalous). Many of the orders have regular 
flowers, but a large number have them two-lipped, 
and therefore irregular, such as the Foxglove, 
labiate plants, and Acanthi 

The following are the orders contained in this 
section : 

*Ericaces — Heathworts. 
*Pyrolace2E — Winter-greens. 
*Montropaceae — Fir-rapes. 

Epacrldacese — Epacrids. 

Ebenaceae — Ebony ordtr. 
*AquifoliaceaE — Holly order. 

Sapotaceaj — Sapotads. 

Myrsinacese — Myrsine order. 

Jasminacese — Jasmines. 
*01eaceae — Olives. 

Salvadoracea — Salvadora order 

Asclepiadaceac — Asclepiads. 
•Apocynaceae — Dogbanes. 

Logan iacea; — Strychnads. 
•Gentianaces — Gentian worts. 

Bignoniacea: — Trumpet-flowers. 

Gesneracea; — Gesnerads. 

CrescentiaceoE — Calabashes. 

Pedaliaceae — Pedalium order. 
•Polemoniaceae — Phlox order. 

Hydrophyllacex— Water- 
leaves. 



Diapensiacea — Diapensia order, 
*Convolvulaceae — Bindweeds. 
*Cuscutacea; — Dodders. 

Cordiaceae — Sebestens. 

* Boraginaceae — Borage worts. 
Ehretiaceae — Ehretia order. 
Nolanaceae — Nolana order, 

*Solanaceae — Potato order. 

*Atropaceae — Nightshades. 

*Orobanchaceae — Broom-rapes. 

*Scrophulariaceae — Figworts. 

•Labiatee or Lamiaceae — Dead 
nettles. 

*Verbenaceae — Verbenas. 
Stilbaceae — Stilbids. _ ' 

Selaginaceae or Globulariaceae— * 

Selagids. 
Acanthaceae — Acanthads. 

* Lentibulariace«e — Butterworts. 

* Primulaceae — Primroses. 
*Plumbaginaceae — Leadworts. 
•Plantaginaceae — Ribworts. 



SYSTEMATIC BOTANY. 



Ericaceae. — This is an extensive order of 
shrubs or under-shrubs, with leaves evergreen, 
rigid, entire, whorled, or opposite, and without 
stipules. 'The name of the heath family,' as it 
has been very appropriately remarked, * conjures 
up immediately the image of a number of narrow- 
leaved plants, with globular, ventricose, or bell- 
shaped flowers ; and we are apt at first to think 
that the family is so natural a one as to require 
very little explanation.' Did the order include 
only the heaths, this would be the case ; for all the 
heaths, differing as they do in some particulars, 
may be recognised at a glance ; but as the order 
includes the Rhododendrons, the Azaleas, and 
Kalmias, besides several other plants which have 
not so strong a family likeness to each other as 
the heaths, it becomes necessary to point out 
the botanical resemblances which conftect them 
together. The first and most striking of these is 
the shape of the anthers — each of which appears 
like two anthers stuck together — and the manner 
of their opening, which is always by a pore or 
round hole in the upper extremijty of each cell. 
The filaments also in all the genera grow from 
beneath the seed-vessel, being generally slightly 
attached to the base of the corolla. There is 
always a single style with an undivided stigma, 
though the capsule has generally four cells, each 
containing several small seeds. The calyx is 
four or five cleft, and the corolla is tubular, with 
a larger or smaller limb, which is also four or 
five cleft. The above are the connecting points 
between the various genera which compose the 
family ; but the differences are such as to require 
a subdivision of the Ericaccce into the following 
sub-orders : i. Ericea, or those most closely 
resembling the true heaths, their fruit being 
loculicidal, rarely septicidal or berried, and the 
buds naked ; 2. RhododendrecB, those allied to 
the Rhododendrons, their fruits being capsular 
septicidal ; the buds, scaly, resembling cones ; 
3. Pyrolece, those allied to the winter-green of 
our woods, and distinguished by having a minute 
embryo at the base of fleshy albumen, the two 
preceding having a cylindrical embryo in the 
axis of the albumen, i. Erice<s. — This sub-order 
may be arranged into two sections — namely, the 
true heaths {Ericida), having bracteal pedicels 
of flowers, the corolla of each flower being more 
or less bell-shaped or globose, with a four-cleft 
limb, a four-lobed calyx, and eight stamens j and 
the Andromedida:, which have the corolla more 
globose, the limb five-cleft, the calyx five-lobed, 
and ten stamens. In other respects both sections 
are nearly alike ; both have a honey-bearing disc, 
and both have the leaves, which are narrow and 
leathery, slightly rolled in at the margin. The 
stamens appear differently in the several genera ; 
some being capitate, others ending in awn-shaped 
horns ; in some they are concealed by the cdrolla, 
in others they are exposed. The style, in some 
of the genera, projects considerably beyond the 
corolla, in others it is rather contracted. The 
more familiar genera are, the common heath of 
our moors {Erica tetralix), common ling or heather 
{Calluna vulgaris), and the Cape heaths, many of 
which have glutinous, cylindrical corollas. The 
genera Andromeda, Zenobia, the strawberry-tree 
{Arbutits), the bearberry of our Highlands {Arcio- 
staphylos uva-ursi), and Gaultheria, frequent in 
gardens, are illustrations of the second section. 



Plants belonging to this sub-order cover large 
tracts of our own country, are common in North 
and South America, and abound at the Cape of 
Good Hope, whidi has supplied our gardens with 
hundreds of the most beautiful species of Erica. 
All of them possess bitter, astringent, and diuretic 
properties ; and the berries of some, as well as 
the flowers, have been used in dyeing. The 
Arbutus is a very ornamental shrub, the berries 
of which are edible, and may be used in the 
preparation of a wine. 2. Rhododendrece.—ThQ 
plants in this sub-order have all less or more 
a resemblance to the well-known genus Rhodo- 
dendron, the species of which have generally ever- 
green leaves, and large showy flowers produced 
in terminal corymbs. The calyx is small; the 
corolla, large in proportion, bell-shaped, and 
deeply five-cleft ; the stamens, five or ten ; the 
capsule, five-celled and five-valved. The flowers 
are generally purple or whitish, though in some 
they are yellow, pink, or bright scarlet, as in the 
Nepaul tree-rhododendron {R. arboreum). The 
genus Azalea is very nearly allied to the rhodo- 
dendron ; but its species — the Indian and Ameri- 
can — differ considerably in their inflorescence and 
leaves ; the latter in some species being deciduous. 
Kalmia and Menziesia are familiar garden genera ; 
Ledum palustre, or wild rosemary, and the 
Labrador tea-plant (Z. latifolium), also rank under 
this section, whose members have an extensive 
range, being found abundantly in Europe, Asia, 
and North America. They are chiefly inhabitants 
of high cold regions, and in this particular agree 
with the general habit of the order. The Rhbdo- 
dendreae possess soporific properties — R. crysan- 
thum being used in gout and acute rheumatism. 
The Azaleas are astringent, and some yield a 
poisonous honey, well distinguishing these plants 
from the true heaths, none of which are poisonous. 
The honey which gave rise to symptoms of 
poisoning in the Greek soldiers during the cele- 
brated Retreat of the Ten Thousand mentioned 
by Xenophon, was obtained from Rhododendron 
ponticum and Azalea pontica, two ornamental 
shrubs much cultivated in our gardens and 
shrubberies. It has been observed that the 
leaves and flowers of R. arboreum poisoned the 
cattle which partook of them in Kumaon ; and 
the leaves of R. ponticum have poisoned sheep 
and goats in this country. Some species yield a 
resinous matter having a powerful and oppressive 
odour. R, setosum is the Tsalu of the Sikkim 
Bhoteas and Tibetans, who attribute the oppres- 
sion and headaches attending the crossing of the 
loftiest passes of the Eastern Himalaya to the 
strongly resinous odour of this and R. anthopogon, 
the Palu of the natives. The Rhododendrons 
introduced by Dr Hooker from Sikkim form the 
most valuable addition to our ornamental plants 
that has been made for many years. R. nivaU 
occurs at elevations of from 16,000 to 18,000 feet 
on the Tibetan frontier. For eight months of the 
year, it is buried under many feet of snow; for 
the remaining four it is frequently snowed and 
sunned in the same hour. R. ferrugineum and 
hirsutum are the roses of the Alps, and form a 
shrubby belt on the Swiss mountains. 3. PyroUa. 
— This sub-order is well illustrated by the winter- 
green {Pyrola), which is common in British woods. 
The species of Pyrola are evergreen plants, with 
white flowers, the corollas consisting of five distinct 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



4 



petals, and which have ten stamens, with anthers 
opening by a pore : the style is single, ending in a 
capitate stigma cut into five lobes; the fruit, a 
five-celled capsule. 

OleacE/E. — Under this order are reckoned 
upwards of 20 genera, and about 130 species. 
They are trees and shrubs with erect or climbing 
stems, and with leaves opposite, petiolate, simple, 
seldom ternate or pinnate, and destitute of stipules. 
The inflorescence is often paniculate ; the flowers 
regular, and sometimes, by abortion, polygamous; 
calyx, free, divided, and persistent ; corolla, hy- 
pogynous, four-cleft, and rarely wanting ; stamens, 
two, alternating with the lateral lobes of the corolla 
when present, or when there are four petals con- 
necting the lateral petals in pairs ; filaments, 
free; anthers, two-celled, bursting longitudinally; 
ovary, free, two-celled ; ovules, pendulous and in 
pairs ; style, sometimes wanting ; stigma, entire 
or bifid ; fruit, fleshy or dry, sometimes one-celled 
by abortion. According to the character of the 
fruit, the order is sometimes subdivided into the 
Ole^e, having it a drupe or berry, and the 
Fraxine^, having it samaroid. 

The principal genera are — Olea, the olive ; 
Fraxinus, the ash ; Ormis, the manna-ash ; 
Ligustrum, the privet ; Syringa, the lilac ; Chio- 
nanthus, the fringe-tree ; and Phtllyrea. The olive 
{O. Europced) is a well-known tree, with small 
white flowers, and a fleshy drupe like a sloe, from 
which is expressed the olive oil of commerce. The 
ash {F. excelsior) is a common British tree, with 
pinnate leaves, the flowers without a corolla, and 
the fruit a winged samara or key, with one or 
two seeds. The manna-ash {Ornns Europced), 
though closely resembling the common ash in its 
leaves and samara, has loose panicles of white 
flowers, the corollas of which are divided into four 
long narrow segments. The privet {Ligustrum 
vulgare), the lilac {Syringa vulgaris), and Philly- 
rea, are too common ornamental shrubs to require 
particular notice. 

Economically, the oliveworts are of great import- 
ance. Besides the oil of the olive, so universally 
used in Europe, the unripe berries are pickled and 
eaten on the continent to provoke an appetite ; and 
the bark, which is bitter and astringent, is used 
as a substitute for cinchona. The bark of the 
common ash, as well as that of several others, is 
astringent and febrifugal, while the wood of the 
former is easily worked, and exceedingly tough 
and durable. What is in the present day called 
manna is a saccharine cathartic, procured by 
wounding the bark of Omus rotundifolia and 
Europcea. The sweetness of this substance is not 
due to the presence of sugar, but to a distinct prin- 
ciple called Mannite, which differs from cane-sugar 
in not fermenting with water and yeast 

L0GANIACE.E. — This order consists chiefly of 
woody plants, with opposite entire, stipulate leaves, 
natives of the tropics. It is chiefly remarkable 
from containing Strychnos Nux-vomica, the plant 
from which strychnine is prepared. It is called 
rat's -bane, poison -nut, or koochla. This tree 
abounds on the Malabar and Coromandel coasts 
of the Indian peninsula, and produces a small 
orange-like fruit full of pulp, in which the seeds 
are imbedded. The latter alone form the fatal 
drug ; but the wood of the tree is intensely bitter, 
and is employed in the cure of intermittent fevers 
and the bites of venomous snakes. Strychnia, the 



alkaloid upon which the poisonous properties of 
the seeds depend, is an intensely bitter substance 
— so bitter, it is said, that its taste can be detected 
when dissolved in 600,000 times its weight in water. 
This has led to its use in the adulteration of malt 
liquors, and there is reason to believe that it is still 
used for this purpose. .5". toxifera is the basis of 
the famous woorali employed by the Red Indians 
to poison their arrows, which thus cause immediate 
death when introduced into the slightest wound. 
S. TieutS yields the upas radja of Java, not that 
half-mythical upas around which so many fearful 
fables have been entwined. 

CoNVOLVULACE^. — A well-defined order, con- 
taining about 670 species. The members are 
lactescent herbaceous plants or shrubs, with stems 
usually twining, and with leaves alternate, undi- 
vided or lobed, and exstipulate. The inflorescence 
is axillary or terminal; peduncles one or many 
flowered, the partial ones generally with two bracts ; 
calyx, persistent in five divisions, and imbricated 
as if in more whorls than one — often very unequal ; 
corolla, monopetalous, hypogynous, regular, decid- 
uous; the limb, five-lobed and plaited; stamens, 
five, inserted into the base of the corolla, and alter- 
nate with its segments; ovary, free, with two or 
four cells; the ovules, definite and erect; style, 
one, usually divided at the top ; stigmas, obtuse or 
acute; capsule, with the valves fitting at their 
edges to the angles of a loose dissepiment, bearing 
the seeds at its base; seeds, large; albumen, 
mucilaginous. 

The more familiar genera are Convolvulus and 
Ipomoea, which have the corolla marked with a 
decided fold or plait, peculiarly imbricated calyx, 
and are climbing plants, not easily confounded 
with any other family. The Convolvulus arvensis 
is the wild climber of our hedges ; and C. tricolor, 
so common in gardens, is a native of Sicily. The 
bindweed {Convolvulus sepium) is another of our 
hedge-natives, and is a well-known pest of the farm 
and garden. The roots of the order abound in an 
acrid, purgative, milky juice, exemplified in jalap 
— which is obtained from Exogonium Purga — and 
in scammony, the concrete juice of the root of Con- 
volvulus Scammonia, the roots or tubers of C. Bat' 
atas, the sweet potato, are edible, as are also those 
of Ipomoea macrorhiza, whose insipid farinaceous 
tubers are found in the sandy soil of Georgia 
and Carolina, weighing as much as forty or fifty 
pounds. 

BORAGINACE^. — The plants of this order are 
chiefly herbaceous, have round stems, alternate 
rough leaves, and flowers in scorpioidal cymes. 
Corolla, usually regular and five-cleft, imbricate, 
often with faucial scales. Fruit, two or four dis- 
tinct achenes ; seeds, exalbuminous. Some of the 
plants of the order yield dyes, such as the al- 
kanet, others form pot-herbs ; one maritime species 
{Mertensia maritimd) is a vegetable substitute for 
oysters, having a similar flavour ; and another 
{Symphytum asperrimum) is particularly recom- 
mended by agricultural writers as a suitable food 
for pigs. More sentimental associations surround 
the forget-me-not {Myosotis palustris), which is 
not uncommon in marshy situations in Britain. 

NOLANACEiE, SOLANACE^, ATROPACE^.— 

These three groups are sometimes associated 
under one order ; and although tabulated separ- 
ately, we shall save space by discussing their 
characteristics together, for they have many points 



SYSTEMATIC BOTANY. 



of structure in common. They are herbaceous 
plants or shrubs, with alternate leaves, and with 
angular or rounded stems ; calyx, five (rarely four) 
parted and persistent ; corolla, with the limb 
having the same number of lobes as the calyx, 
somewhat unequal, and deciduous ; estivation, 
folded or imbricate ; stamens, alternating with 
the segments of the corolla, sometimes one abor- 
tive; anthers, bursting longitudinally, or by ter- 
minal pores ; ovary, two or more celled, rarely 
one-celled ; ovules, usually indefinite ; style, con- 
tinuous ; stigma, obtuse, very rarely lobed ; fruit, 
either a capsule opening variously, a berry with 
the placenta adhering to the dissepiment, or a 
nuculanium, with five spurious-celled nucules, 
which have one seed in each ; seeds, sessile. 

The Solanacece closely resemble each other in 
their flowers, and also in their berry-like fruit, 
which is always crowned by the persistent calyx ; 
seeds, albuminous ; embryo, curved. The estiva- 
tion is valvate or induplicato-valvate. The genus 
Solanum, to which belongs the bitter-sweet {S. 
Dulcamara), the garden nightshade {S. nigrum), 
and the potato {S. tuberosum), has the anthers 
opening by pores like the heaths ; whereas all 
the other members have a slit down each cell, 
as the tomato, or love-apple {Lycopersicum escu- 
lentum), with its edible fruit ; the capsicum (C 
frutescens, &c.), whose dry inflated berry yields 
the cayenne-pepper of commerce ; and the winter- 
cherry {Physalis Alkekengt), also with edible 
berry-like fruit. To the Atropacecz belong the 
deadly nightshade or dwale {Atropa Belladona), 
which furnishes the deadly poison of that name ; 
and the Barbary or box-thorn {Lyciutn barbarum). 
They are dangerous in their qualities, the leaves 
and flowers being narcotic and poisonous. They 
are distinguished from the preceding principally 
by the more or less imbricated estivation of the 
corolla ; it is never valvate. The flowers are also 
more funnel-shaped, with a longish tube and 
spreading limb. The principal genera are — Nico- 
tiana, N. Tabacum, being the Virginian tobacco 
of commerce, and N. persica is the source of 
Shiraz or Persian tobacco, so much esteemed by 
smokers. Petunia, which furnishes some of our 
best known garden favourites ; Nierembergia, a 
genus of ornamental green-house plants ; Hyos- 
cyamus, the poisonous henbane ; Datura, D. 
Stramonium, being the common thorn-apple ; and 
Brugmansia and Salpiglossis, all more or less 
prized for their showy funnel-shaped flowers, some 
of which are highly fragrant. The plants of this 
order display marked narcotic properties, and 
cause dilatation of the pupil. Nolanacece. — * This 
tribe,' says Loudon, ' is principally known by the 
genus Nolana, the species of which are annual 
plants, natives of Chili and Peru, which have of 
late been much cultivated in British gardens. 
The flowers of N. atriplicifolia, one of the com- 
monest kind, very much resemble those of the 
Convolvulus tricolor, and the leaves are large and 
juicy like those of the spinach. On opening the 
corolla there will be found five stamens, surround- 
ing four or five ovaries, which are crowded together 
on a fleshy ring-like disc. These ovaries, when 
ripe, become as many drupes, enclosing each a 
three or four celled nut, which is marked with 
three or more grooves on the outside, and has 
three or more little holes beneath. All the 
species of Nolana have the same peculiarities in 




the 



Foxglove, 
well-known snap- 



their seed-vessels, though they differ in many 
other respects.' 

SCROPHULARiACEiE.— The Figworts, of which 
the common foxglove may be taken as the type 
form rather an extensive order, consisting of about 
170 genera, and 1800 species. The plants are 
herbaceous, rarely shrubby, with round or square 
stems ; the leaves being simple and exstipulate, 
opposite or whorled, seldom alternate, and either 
sessile or with footstalks. The inflorescence is 
veiy variable, being axillary or united, usually in 
spikes, racemes, or in panicles ; calyx, inferior, 
persistent, and often unequal ; corolla, tubular or 
inflated, with a short 
limb, which is flat or 
erect, nearly equally 
divided, or labiate ; 
stamens, definite, two 
or four (didynamous), 
rarely five, filaments, 
free ; anthers, two- 
celled ; ovary, two- 
celled ; style, simple ; 
stigma, obtuse, rarely 
bifid ; fruit, a dry cap- 
sule, rarely baccate. 

The following genera 
may be mentioned as 
illustrative of the order : 
Scropkularia, weeds 
common in Britain. 
Digitalis, the foxglove 
of our waysides and 
gardens ; Antirrhinum, 

dragon ; Linaria, the toad-flax of our hedges aiid 
banks ; Euphrasia, the eyebright ; Veronica, in- 
cluding the brooklime and the speedwells ; Rhin- 
anthus, the yellow rattle, Verbascum, the mullein ; 
and Calceolaria, Buddlea, Mimulus, and others, 
now favourites in every flower-garden. The form 
of the flowers in the diflierent genera varies con- 
siderably, as may be seen by examining the fox- 
glove, the speedwell, and calceolaria — plants at 
the command of every one. The stamens also 
present considerable differences : in the foxglove 
{Digitalis purpurea) there are two long and two 
short ; in Pentstetnon there are five, the fifth being 
long and slender, and without an anther ; in Cal- 
ceolaria and Veronica there are only two. Various 
attempts have been made to subdivide the order 
— as, for example, into two sections, the one 
including the genera having four anther-bearing 
stamens, and the other those having only two- 
anthered stamens. Mr Bentham divides it into 
three sub-orders, according to the inflorescence, 
each of which is again subdivided into several 
tribes. 

The majority of this family contain a principle 
more or less acrid, purgative in some, and poison- 
ous, as in the foxglove, unless taken in small doses. 
The meadow eyebright {Euphrasia officinalis) is 
slightly astringent and aromatic, without the 
deleterious qualities of the other genera. Cows 
are said to be fond of MelamPyrum prat£nse ; and 
Linnaeus says the best and yellowest butter is 
made where it abounds. One or two species of 
Linaria and Calceolaria are named as yielding 
colours for the dyer. Mimulus luteus affords an 
interesting example of an exotic plant— from 
America — becoming speedily diffused throughout 
Europe in a naturalised state. It is now not 
*^ 103 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




Labiatce. 



uncommon in ditches. Its stigma, formed of two 
lips, displays peculiar irritability. 

Labiate. — A very large natural order, remark- 
able for the uniformity of structure and properties 
which prevails among the members. The labiate 
or lipped corolla immediately suggests the mint, 
sage, thyme, dead-nettle, horehound, and lavender, 
with which every one must be more or less familiar. 
They are herbs or under-shrubs, with quadrangular 
stems, and opposite, divided or undivided, exstipu- 
late leaves, replete with receptacles of aromatic 
oil. The flowers are in oppo- 
site, nearly sessile, axillary ver- 
ticillasters, resembling whorls, 
as in the dead-nettle ; some- 
times solitary ; calyx, tubular 
and persistent ; corolla, bilabi- 
ate, the upper lip {a) being 
entire or bifid, the lower (p) 
three-cleft, the upper in estiva- 
tion overlapping the lower ; 
stamens, four, didynamous, the 
upper sometimes wanting ; ovary, deeply four- 
lobed, seated on a fleshy disc, each lobe containing 
one erect ovule ; style, simple ; stigma, bifid ; 
fruit, from one to four small nuts inclosed within 
the persistent calyx. 

The following plants well exemplify the order : 
Lamhtm album, the white dead-nettle of our wall- 
sides ; Salvia officinalis, the common garden sage ; 
Rosmarinus officinalis, the well-known rosemary 
shrub ; Thymus Serpyllum, the wild thyme ; Lav- 
andula vera, the sweet-scented lavender ; Mentha 
viridis, spearmint, and M. piperita, peppermint ; 
M. sylvestris is the Greek Heduosmon, translated 
mint in Scripture ; Nepeta Glechoma, the ground 
ivy ; Marrubium vulgare, the true medicinal hore- 
hound ; Ballota nigra, black horehound, well 
known for its heavy oppressive smell ; Primella 
vulgaris, self-heal ; Ajuga reptans, the common 
bugle ; with basil, marjoram, betony, hyssop, and 
other culinary and medicinal herbs. 

ACANTHACEiE. — There are nearly loo genera 
enumerated under this order, and upwards of 1400 
species of herbs and shrubs, principally inhabiting 
tropical regions. Leaves, simple, opposite, and 
without stipules ; inflorescence, terminal or axil- 
lary ; flowers, showy, in spikes with two or three 
bracts to each ; calyx, in four or five divisions, 
and persistent — but in many of the species incon- 
spicuous or obsolete, its place being supplied by 
the large bracts ; corolla, monopetalous, and 
usually irregular, with the limb ringent or bilabi- 
ate, and deciduous ; stamens, two or four, and in 
the latter case didynamous ; anthers, one or two 
celled, sometimes bearded, as in Acanthus, and 
bursting longitudinally ; style, simple ; stigma, 
one or two lobed ; fruit, a two-celled capsule, 
elastically two-valved ; seeds, supported on a fili- 
form podosperm. The elastic dehiscent capsules, 
wingless seeds with hooked dissepiments, and 
imbricated flowers, are distinguishing features. 

Examples of the genera are — Acanthus, Thun- 
hergia, Gold/ussia, Lankesteria, Ruellia, and yus- 
ticia. The species of Acanthus are found chiefly 
in the south of Europe ; they are plants with 
graceful foliage, and the leaves of the A. mollis is 
said to have furnished Callimachus with patterns 
for the capital of the Corinthian pillar. The 
corolla varies considerably in the different genera ; 
being bilabiate in Justicia, funnel-shaped in Ruel- 



lia, and campanulate in Thunbergia, the species 
of which are exotic climbers. 



% 




Acanthus. 

The properties of the order are little known. 
The Arabs use the leaves of an Acanthus by way 
of salad ; yusticia pectoralis, boiled in sugar, 
yields a syrup used in the West Indies as a 
stomachic ; and J. patiiculata is said to be the 
basis of the famous French tonic. Drogue Amere. 
A valuable deep blue dye is said to be obtained 
from one of the East Indian Ruellias. 



MONOCHLAMYDEiE. 

The plants in this division have either no floral 
envelope, or have one only. In the former case, 
the pistil and stamens are naked ; in the latter, 
they are surrounded by a calyx, there being no 
parts corresponding to the petals of a true corolla. 
The following are the orders : 

ANGIOSPERMiE. 
Nyctaginaceae — Marvel of Peru *Empetracese— Crowberries. 



order. 

*Amaranthaceae — Amaranths. 
*Chenopodiaceae — Goosefoots. 

Basellacese — Basella order. 
*Scleranthacex — Knawel order. 

Phytolaccaceae — Phytolaccads. 

Petiveriaceae — Petivera order. 
*Polygonaceae — Buckwheats. 

Begoniaceae — Begoniads. 

Lauraceae — Laurels. 

Atherospermaceae — Plume Nut 
megs. 

Myristicaceae — Nutmegs. 

Monimiaceae — Monimia order. 

Proteaceae — Protea order. 
*Elaeagnaceae — Oleaster. 

Penseaceae — Penaea order. 
*ThymeIaeaceae — Mezereons. 

Aquilariaceae — Aquilaria order. 



*Euphorbiaceae — SpurgewortS. 

Scepaceae — Scepa order. 
•Callitrichacex — Starworts. 
•Ceratophyllaceae — Horn worts. 
*Urticaceae — N ettle worts. 

Artocarpacese — Bread-fruits. 
*Ulmaceae — Elms. 

Stilaginaceae — Stilago order. 

Lacistemaceae — Lacistema or- 
der. 

Podostemonaceae — River- weeds. 

Chloranthacea: — Chloranthads. 

Saururaceae — Lizard's tails. 

Piperaceae — Peppers. 
"Myricaceae — Gale order. 
*SalicaceaE — Willows. 

Altingiaceae — Liquidambars. 
•Betulaceae — Birches. 

Corylaceae — Hazels and Oaks. 



Chailletiaceae — Chailletia order. Casuarinaceae — Beefwoods. 



Samydaceae — Samyda order. 

Homaliaceae — Homalium order. 
" Santalaceae — Sandal-wood s. 
•Aristolochiaceac — Birthworts. 

Nepenthaceae — Pitcher plants. 

Datiscaceae — Datisca order. 



Platanaceac — Plane-trees. 
Juglandaceae — Walnuts. 
Garryace^ — Garrya order. 
Rafflesiaceae — Raffle.sia order. 
Cytinaceae — Cistus Rapes. 
Balanophoracea; — Balanophoras. 



*ConiferaE — Pines 

bearers. 
*Taxaceae — Yews. 



GYMNOSPERMiB. 

ir Cone- Gnetaceac — ^Jointed Firs. 

Cycadaceac — Cycad and Zamia 
order. 



SYSTEMATIC BOTANY. 



ANGIOSPERM^ 



CHENOPODIACE^.— Chiefly herbs with herba- 
ceous (greenish) flowers. The embryo is coiled 
round mealy albumen, or spiral without albumen ; 
ovary, free, one-celled ; stamens, inserted into the 
base of the perianth. Many of the species are 
used as pot-herbs, such as Spinach, Orach, and 
English mercury {Chenopodium Bonus-Henricus). 
The seeds of C. Quinoa are used as food. The 
Beet {Beta vulgaris) yields a large proportion 
of sugar, and in the form of mangold-wurzcl is an 
important forage plant throughout Europe. 

Laurace/E. — An important order, comprising 
about 450 species. They are tropical trees, with 
elegant foliage and aromatic properties, having 
exstipulate, alternate (seldom opposite) leaves, 
with inconspicuous flowers. The perianth is from 
four to six cleft, the limb sometimes obsolete ; 
estivation, imbricate. The male and female 
flowers are distinct : the former have four, six, or 
eight stamens, opposite the segments of the peri- 
anth ; the latter have four or more abortive sta- 
mens, furnished with glands, but without anthers, 
a one-celled, one-seeded ovary, with a simple 
style and an obtuse-crested stigma. The fruit is 
fleshy and indehiscent, naked, or covered by the 
enlarged and fleshy perianth. The two or four 
celled anthers, with the valves curling upwards 
when ripe, and the filaments furnished with kid- 
ney-shaped glands at their base, are character- 
istics of the order. 

The chief genera are — Laurus, the sweet bay ; 
Sassafras, the sassafras-tree ; Persea, the avocado- 
pear ; Camphora, the camphor-tree ; Cinnamo- 
miim, the cinnamon-tree ; Cassytha, the Dodder- 
laurel ; Tretranthera, and Cryptocarya. The true 
laurels have two anthers, and naked fruit ; the 
cassia, cinnamon, and camphor have four anthers, 
and the fruit covered. The plants contain essen- 
tial oil in abundance, which imparts to them a 
peculiar sweet, though strong penetrating odour, 
and a warm and pleasant taste ; hence they yield 
some of our most grateful stimulants and spices. 
Cinnamon, cassia, camphor, benzoin, and sassa- 
fras are products of the family ; the roots of the 
sweet bay yield a violet dye ; and a concrete oil, 
used in candle-manufacture, is obtained from 
the fruit of Laurus glauca. The branches of 
Latirus nobilis, or sweet bay, were used to crown 
the victors in the ancient games. This plant 
seems to be the ezrach of the Bible, translated 
' green bay-tree.' 

ARiSTOLOCHiACEiE. — There are only six or 
eight genera in this order, the members of which 
are herbaceous plants or shrubs, of climbing 
habit. The characters are — flowers, hermaphro- 
dite ; perianth, tubular, adherent with the ovary, 
and divided into three segments ; stamens, from 
six to twelve epigynous, sometimes free and dis- 
tinct, in other cases adhering with the style and 
stigma ; ovary, three to six celled ; style, short ; 
stigma, six-rayed ; fruit, capsular, dry, or succu- 
lent, three to six celled, and many-seeded ; seeds, 
thin, flat, and of a dark-brown colour. 

The chief genera are — Aristolochia, the birth- 
wort ; and Asarum, the wild-ginger of North 
America. Many of the species are natives of 
Europe ; but they abound in the tropical regions 
of South America ; Arist. Clematitis (common birth- 



wort) and Asar. Europaum (Asarabacca) are the 

only two found in Britain, and are doubtfully 

native. ' 

The birthworts are heating and stimulating in 




Aristolochia. 

their properties, and act chiefly on the skin and 
kidneys. The prepared root oi Arist. scrpentaria 
(Virginian snake-root) is used in ag^e, typhus 
fever, and in gout — being one of the ingredients of 
the celebrated Portland powder. The snake-root 
is regarded as an antidote against serpent-bites. 
A drop or two of the juice, if introduced into the 
mouth of one of these reptiles, has the power of 
stupefying it, so that it can be handled with 
impunity ; and a few drops swallowed almost 
instantly cause death. The roots of the species 
of Asarum have bitter and acrid properties, and 
a disagreeable odour like that of the stapelias. 
Asarum canadense has an aromatic flavour, and 
is often used by the country-people in lieu of the 
true ginger. 

EuPHORBlACEiE. — In Britain, this order is 
represented by the small weedy spurges of our 
gardens and waste grounds, but exhibits a nobler 
aspect in hot regions, where the tall cacti-like 
columnar species attain gigantic proportions. 
The juice is usually acrid and milky, and the 
fruit formed of three globose carpels in union. 
The purgative resin Euphorbium is supplied by 
E. officinarum and other species. Hura crepitans 
is the sand-box tree, whose fruit bursts with a 
loud noise. Ricinus communis yields castor-oil. 
The vegetable tallow of China is derived from 
Stillingia sebifera. The seeds are beaten down 
and boiled to separate the tallow, which fuses at 
80°, and is used for candles. Aleurites triloba 
yields Eboe-oil, used by artists. Croton Tiglium 
seeds yield croton-oiL jFanipha tnanihot is the 
cassava or manioc plant of the West Indies. 
yatropha Curcas produces the physic-nut. Old- 
fieldia Africana is the tree which supplies the 
African teak or oak. 

UrticacEvE — ARTOCARPACEiE. — These are ex- 
tensive orders of plants, which, to the uninitiated, 
may appear very dissimilar — as illustrated, for 
example, by the common nettle, the hop, the 
hemp, the pellitory of the wall, the bread-fruit tree, 
the cow-tree, upas, mulberry, common fig, banyan, 
and India-rubber tree, all of which, though ex- 
hibiting different habits and products, are not 
only strikingly alike in their essential characters. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



but ako in their general properties. They are 
much simplified by subdivision into two orders — 
namely, UrticacecB and Artocarpacea — the former 
including the herbaceous species — as the nettle, 
hemp, and hop, with watery juice ; and the latter 
the ligneous species — as the bread-fruit, mulberry, 
and fig, which have their juice milky. Bearing 
this distinction in mind, the following may be 
stated as the characteristics common to both : 
Trees, shrubs, or herbs, with alternate leaves, 
sometimes covered with asperities or stingfing 
hairs, and furnished with membranous stipules, 
which are deciduous or convolute in vernation ; 
flowers, usually monoecious, sometimes dioecious ; 
perianth, membranous, lobed, and persistent ; 
stamens, definite, distinct, inserted into the base 
of the perianth, and opposite its lobes ; anthers, 
turned backwards with elasticity when bursting; 
ovary, superior, simple ; ovule, solitary, erect, or 
pendulous ; stigma, simple ; fruit, a simple inde- 
hiscent nut, as in the nettle and hemp — or con- 
sisting of achenes immersed in a fleshy recep- 
tacle, or the persistent fleshy perianths, as in the 
bread-fruit, or inclosing them within its cavity, as 
in the fig. 'The unisexual flowers,' says Dr 
Lindley, 'simple lenticular fruit, and superior 
radicle and stipules, aff"ord the essential char- 
acteristics of this order, which cannot well be 
mistaken for any except Chenopodiacecej and the 
plants of that order never have stipules, or rough 
or stinging leaves.' 

The chief genera in the order URTiCACEiE are 
— Urtica, of which U. dioica is the common 
stinging-nettle ; U. urens, the smaller stinging- 
nettle ; and U. pilulifera, the Roman nettle ; 
Humulus Itipulus, the cultivated hop ; Cannabis 
sativa, the fibrous hemp of commerce ; and Pari- 
etaria erecta, the pellitory of the wall. The 
members of this order are widely scattered over 
the world, and increase apparently with the pro- 
gress of civilisation ; some of them — as, for 
example, the nettles — following in the footsteps 
of man. The chief genera of the order Arto- 
CARPACEiE are — Artocarpus, of which A. incisa is 
the bread-fruit of the South Sea Islands ; and 
A. integrifolia, the jack-tree of the East India 
Islands ; Galactodendron utile, the cow-tree or 
palo de vaca of South America ; Antiaris toxi- 
caria, the upas-tree of Java, about which so many 
fabulous stories have been told ; Morns, of which 
M. nigra is the common black mulberry, M. 
rubra, the red, and M. alba, the white mulberry, 
the leaves of which are so much esteemed for 
feeding silkworms ; Ficus, of which F. Carica is 
the common edible fig, F. Sycamorus, the syca- 
more fig, the wood of which is very durable, and 
is supposed to have been used in the construction 
of mummy-cases ; Urostigina, of which U. Indica 
is the spreading banyan, U. elasticum the India- 
rubber tree, and U. religiosum the sacred fig or 
pippul-tree of India. Baehmeria {Urtica) nivea, 
the China nettle, is the source of that beautiful 
fabric for handkerchiefs, &c. which has of late 
years come into use under the name of China- 
grass and China nettle-fibre. Large quantities 
of the fibre are produced in the East, and find a 
ready sale in European markets, and especially 
among European residents in hot countries, for 
whose clothing this extremely fine fibre is peculi- 
arly adapted. 

The Urticaceae have watery juice, which is 

106 



acrid and astringent, and the fibres of their stems 
are all less or more tenacious. The leaves of the 
hemp are narcotic ; the hop (fig.) has bitter, aro- 



,U^>s/^A A^^ 



Hop. 



matic, and stomachic properties, and its effluvia 
are said to be narcotic. The stinging property of 
the common nettle is well known. In the Artocar- 
paceae, the juice is milky, and on exposure to the 
air, becomes tough and elastic. Their fruit is 
edible, but their juice is generally acrid and 
poisonous ; except in that of the Galactodendron, 
which is wholesome and nutritious. The elabor- 
ation of a tough elastic product seems to be char- 
acteristic of the whole order — making its appear- 
ance in the stem of the hemp, in the inspissated 
juice of the India-rubber tree, or in silk, the best 
of which is derived from silkworms which feed 
on the leaves of the mulberry. 

Betulace^e. — A small order of trees and shrubs, 
abounding in the temperate and colder regions of 
the globe. They have alternate simple leaves, 
with the primary veins often running straight from 
the midrib to the margin, and deciduous stipules. 
The flowers are in catkins, unisexual, and monoe- 
cious ; the males having small scales in place 
of a perianth, or, in Alnus, a four-leaved mem- 
branous perianth. Stamens distinct, opposite the 
scales, scarcely ever monadelphous ; anthers, two- 
celled ; ovary, two-celled ; ovules, definite, pen- 
dulous ; style, single or none ; stigmas, two ; fruit, 
membranous, indehiscent, by abortion one-celled ; 
seeds, pendulous, naked. 

The chief genera are Betula, the birch, and 
Alnus, the alder, the species of which abound in 
every northern country. The common white birch 
{B. alba) is an elegant tree, thriving in almost any 
sort of soil, and becoming stunted and dwarfish 
only in the arctic regions, or at great elevations. 
The weeping-birch is a still more graceful tree, 
grown in lawns and parks for its fine drooping 
branches and neat foliage. B. nana is the dwarf 
birch of high and exposed situations, being found 
on the Scottish mountains and in some countries 
approaching to the very limits of perpetual snow. 
B. nigra is the black birch of North America, 
the timber of which is used by cabinet-makers ; 
and B. papyracea is the paper birch, whose bar! 




SYSTEMATIC BOTANY. 



is used by the Esquimaux and others in the con- 
struction of canoes. The common alder (A. 
glutinosa) is a quick-growing tree, found in 
swampy flats and by the borders of streams ; its 
wood resists well the action of water, and is useful 
for piles ; the Rialto at Venice is built on alder- 
piles, as well as many houses in Amsterdam ; the 
hoary alder {A. tncana) is seldom found south 
of the sixtieth parallel ; the notch-leafed alders 
{A. sinuolata and A. glaucd) are both American 
species. 

The bark of the order is astringent and bitter. 
A decoction of birch-bark is used by the Lap- 
landers in the preparation of reindeer skins ; and 
the empyreumatic oil derived from it is used by 
the Russians in tanning, which gives the peculiar 
odour of their leather. The sweetish sap obtained 
by tapping the birch in spring is the chief ingredient 
in birch-wine ; the leaves, which, when young, 
are highly odorous, are also used in imparting 
dyes of vaiious shades of yellow. B. lenta yields 
sugar. 

CoRYLACEyE. — The Corylaccae or Cupuliferae are 
so named from the cup-like shape of the persistent 
involucre in which their fruit or nuts are placed — 
as, for example, the acorn. The order includes 
many genera of well-known trees and shrubs — as 
the oak, Spanish chestnut, beech, hazel, and horn- 
beam. Their leaves are alternate, simple, and 
stipulate ; their venation well marked, and often 
rigid ; flowers, unisexual ; the males in catkins, 
and the females in clusters or in catkins ; the male 
flowers have from five to twenty stamens inserted 
into the base of the scales, or of a membranous 
perianth, generally distinct ; in the females, the 
ovaries are crowned by the rudiments of an 
adherent perianth, seated within a coriaceous 
involucre of various figure, and with several cells 
and several ovules, most of which are abortive ; 
ovules, twin or solitary, pendulous ; stigmas, seve- 
ral, nearly sessile, and distinct ; fruit, a bony or 
leathery nut, of one cell, and more or less inclosed 
in the involucre. 

The following are the most familiar genera : 
Quercus, of which Q. pedunculata and sessiliflora 
are the British oaks ; Q. suber, the cork-tree ; Q. 
Ilex, the evergreen oak ; Q. rubra, the scarlet oak 
of America ; Q. infectoria, the gall-yielding oak ; 
and Q. cocci/era, the kermes oak. Fagus, of which 
F. sylvatica is the common beech of our woods ; 
and F. ferruginea, of North America, has edible 
fruit. Castanea, to which belong C. vesca, the 
edible sweet chestnut ; and C. ptimila, the dwarf 
Virginian chestnut. Coryhis, of which C. Avel- 
lana is the common hazel-nut or filbert, which 
yields an oil used by artists and watch-makers. 
Carpinus Betultis, the hornbeam of our hedges ; 
and Ostrya Virginica, the iron-wood of America. 
The hornbeams are by some botanists ranked 
under the Birch tribe, on account of the involucre 
not forming so complete a cupule as the other 
genera ; but this seems too minute a distinction, 
as the involucre is not more leafy than it is in 
some of the filberts. The members of the family 
abound in Europe, Asia, and North America, and 
generally in temperate regions, more sparingly in 
South America ; they are altogether absent from 
the south of Africa. 

The bark in all the species is bitter and astrin- 
gent, and is used for dyeing, tanning, and for 
medical purposes. In a few, the fruit is bitter 



and disagreeable ; but in the majority it is farina- 
ceous, and frequently contains an oily matter, used 
in domestic economy. Their fruit, as well as their 
bark and timber, is of the highest value to man. 
The gall-nut is an excrescence of the oak caused by 
the puncture of an insect ; it is used in medicine, 
and in the manufacture of ink and black dyes. 

GYMNOSPERMiE. 

CoNlFERiE.— One of the most important, as it 
is one of the best defined, of the natural orders. 
Its members are trees or shrubs, with a sym- 
metrically branched trunk abounding in resin, 
and are familiarly illustrated by the Scotch pine, 
the spruce and silver firs, the larch, the cedar, 
the araucaria, the arbor vitas, the cypress, and the 
juniper. The ligneous tissue of their wood is 
marked with circular discs having a central 
punctation ; their leaves are linear, needle-shaped, 
or lanceolate, entire at the margin. The charac- 
ters afforded by the fructification are : Flowers, 
unisexual ; males in deciduous catkins, monan- 
drous or monadelphous, each floret consisting of 
a single stamen, or of a few ; females in cones, 
whose scales arise from the axil of membranous 
bracts supplying the place of ovaries ; destitute 
of a proper style or stigma ; ovules, naked, in 
pairs on each scale, with large micropyles at 
their apices ; fruit consisting of a cone formed 
of the hardened scales, which become enlarged 
and indurated, and occasionally of the bracts 
also ; seed, with a hard crustaceous testa. In 
speaking of the Coniferas, it has been not inaptly 
remarked that ' the flowers are quite different from 
what is generally understood by that name, being 
in fact nothing but scales ; those of the male con- 
taining the pollen in the body of the scale, and 
those of the female producing the ovules or in- 
cipient seeds at the base.' 

Well defined as the order obviously is, there 
are minor distinctions which warrant its sub- 
division into the following sections — namely, 
AbietinE/E, the true pines and firs ; and Cu- 
PRESSlNEiE, the cypresses. In the firs, the fruit 
is a cone, the scales of which open, and more 
or less recurve, when the seeds are ripe ; the 
ovules are inveited ; the pollen, oval, or curved : 
in the cypresses, the fruit is also a cone, but 
rounder, and with fewer scales, occasionally 
succulent, forming a galbulus ; ovules, erect ; pol- 
len, spheroidal. Of the Abietineae the following 
are characteristic members : Pinus sylvestris, the 
Scotch pine ; Abies excelsa, the spruce-fir; J'icea 
pectinata, the silver fir ; Larix Europcea, the com- 
mon larch ; Cedrus Libani, the cedar ; and Arau- 
caria imbricata, the Chili pine — all of which arc 
evergreens, with the exception of the larch. The 
Cupressineas are well represented by Cupressus 
sempervirensy the evergreen cypress ; Thuja occi- 
dentalis, the American arbor vitaj ; Taxodium 
distichum, the deciduous cypress ; Juniperus com- 
vtiinis, the juniper of our moors ; J. sabina, the 
savin-tree, as well as by the newer genera, Saxe- 
Gothcea, Fitzroya, &c. 

The high importance of this order is derived 
from its timber, which in all is straight, easily 
worked, and durable. Wellingtonia gigantea, the 
mammoth tree of California, forms a lofty trunk 
112 feet in circumference, and upwards of 350 
feet in height. Many valuable additions have 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



been made to this order of late years by Douglas, 
JefiFrey, Murray, Brown, and others. Vast forests 
of pines occur in North America, which have 
yielded many species well adapted to our climate, 
such as Abies Douglasii, Pattoniana, Pinus Bal- 
fouriana, APNabiana, Jeffreyi, &c. ; and indeed 
almost every gentleman's estate exhibits examples 
of this order, not only from America, but from 
almost every region in the world. The deodar and 
cedar, from the East ; firs, cypresses, and juni- 
pers, from the Far West ; araucarias, from Chili 
and the antipodes ; and cryptomerias, from Japan, 
form by far the most interesting, the most useful, 
and the most ornamental of our forest trees, 
whether planted merely with a view to the raising 
of timber, or for the purpose of beautifying the 
landscape. (See Arboriculture.) Many plants 
of the order are also valuable for their resinous 
productions ; several kinds of pitch, tar, turpen- 
tine, g^ms, and balsams being procured from 
them. The large seeds of some are edible and 
wholesome ; the succulent cones, or, as they are 
familiarly called, berries of the juniper are largely 
used in the preparation of gin ; and the main 
ingredient in spruce-beer is an extract from seve- 
ral species of Abies. Great tanning-powers exist 
in the bark of the larch ; the savin, juniper, and 
others, possess stimulating and diuretic properties. 
Taxace^. — The yews are nearly related to 
coniferae, and are usually associated with them. 
They differ in not producing true cones. The 
wood of many species is also peculiar, having 
spirals on the woody tubes, as well as discs ; but 
this we have recently ascertained to be also the 
case in some firs — such as Abies Dous'lasii. 



ENDOGENOUS OR MONOCOTYLEDONOUS 
PLANTS. 

This class includes those plants whose leaves 
have their veins placed parallel — as the palms, 
the grasses, the hyacinth and crocus, and whose 
stems have no distinction of pith, wood, bark, 






Sections of Dicotyledonous and Monocotyledonous 
Stems. 

concentric circles, and medullary rays, like the 
Exogens {a), but consist merely of a confused 
mass of tissue {b). Their seed contains an 
embryo, having only one seed-lobe or cotyledon ; 
hence the term Monocotvledon. Their trunks 

108 



increase inwardly, instead of by external conceni 
trie layers ; hence also the term Endogen. They" 
are divided into three sections— DiCTYOGENyE, 
differing from all the others in having the leavesj 
more or less net-veined, and usually articulate ' 
with the stem. Petaloide^e, or Florid^e, those' 
having a perianth — such as the orchis, lily, palm, 
&c. Glumifer^, those which are destitute of a 
perianth, but have glumes or husks instead, like 
the grasses. The trees of this division are strictly 
tropical ; the herbaceous species are found aU 
over the globe. 

§ I. DICTYOGEN^ 



*Dioscoreaceae— Yam order. 
Smilacex — Sarsaparilla order. 
•Trilliacese— Trillium order. 



Roxburghiaceac — Roxburghia or- 
der. 
Philesiaceae — Philesia order. 



§ 2. PETALOIDE.^ 



•Hydrocharidaceae — Frog-bits. 
'OrchidacesE — Orchids. 

Apostasiaces — Apostasia order. 

Burmanniacex — Burmannia or- 
der. 

Zingiberaceae — Ginger order. 

Marantaceae — Arrow-roots. 

Musaces — Bananas. 
•Iridaceae — Iris order. 
•Amaryllidacese — Amaryllis or- 
der. 

H ypoxidaceae — Hypoxids. 

Hsemodoracesc — Blood-roots. 

Taccaceac — Tacca order. 

Bromeliaceae — Pine Apples. 
*LiliaceaE — Lilies. 
•Melanthaceae — Colchicum or- 
der. 

Gilliesiaceas — Gilliesia order. 

Pontederiaceae — Pontederia or- 
der. 



Xyridaceae — Xyris order. 

Philydracese— Waterworts. 

Commelynaceae — Spiderworts. 

Mayacacca;— Mayaca order. 
* J uncaceae — Rushes. 

Palmacex — Palms. 
•Alismaceae— Water-plantains. 
•Juncaginacejc— Arrow grasses. 
•Butomaceae — Flowering-rushes. 

Pandanaceac— Screw-pines. 
*Typhaceac — Bulrushes. 
*Araceac — Arum order. 
•Orontiacea: — Sweet Flags. 

Pistiaceae — Duck-weeds. 
•Naiadaceae — Pond-weeds. 

Triuridaceae— Triuris order. 
*Restiaceae— Restio order. 
*Eriocaulonaceae — Pipeworts. 

Desvau.\iacece — Bristlcworts. 



§ 3. GLUMIFERiR 
*Cypetacese — Sedges. *Gramineae— Grasses. 

DICTYOGENiE. 

Dl0SC0REACE.(E. — These are twining, somewhat 
shrubby plants, with unisexual flowers in spikes, 
natives of the tropics, except Tavius comtnunis^ 
or Black Bryony, which represents the order in 
temperate climates. Various species of Dioscorea 
yield edible tubers, which are known by the name 
of yams, and are used like potatoes. D. Batatas 
is the Chinese Potato. Testiiditiaria Elephantipes 
is the Elephanfs-foot, Hottentot's-bread, or Tor- 
toise plant, of the Cape. 

PETALOIDEiE. 

ORCHlDACEiE. — This order consists of terrestrial 
or epiphytal herbaceous plants with enlarged roots 
and stems. The roots in epiphytal species are 
clothed with an outer layer of spiral cells, which 
apparently serve the purpose of absorbing moisture 
from the atmosphere, and thus enabling the plant, 
which has no roots in the soil, to subsist and 
develop itself. The perianth consists of six seg- 
ments in two rows, one differing in form from the 
rest, and called the labellum. The pollen-cells do 
not occur in the form of distinct grains, but are 
aggregated together in simple or compound masses, 
which become detached collectively. The flowers 
often resemble the forms of insects, as the bee 
orchis of Kent, and the more gaudy butterfly 
orchid of the tropics. The singular forms and 
intense colours of their flowers recommend these 
plants to the attention of horticulturists. Of the 
3000 existing species, few are conspicuous for their 
uses. Species of Eulophia furnish salep ; and the 
fragrant vanilla, used in confectionary and in the 



SYSTEMATIC BOTANY. 



preparation of chocolate, is obtained from Vanilla 
planifolia and aromatica. 

Bromeliace^. — Thiis family consists of about 
a dozen genera, and more than 170 species of 
plants, with scarcely any stem, and sometimes 
epiphytic in their habit. Their leaves are rigid, 
channeled, and often spiny or toothed at the 
margin. The perianth is tubular, its parts in two 
rows ; the outer, or calyx, in three clefts, rigid, 
and persistent ; the inner, petaloid and deciduous ; 
stamens, six, inserted into the tube of the perianth ; 
ovary, free or cohering, and three-celled ; ovules, 
indefinite ; style, single ; stigma, three-parted, 
often twisted ; fruit, capsular or succulent, three- 
celled, and many-seeded. 

The principal genera are — Bromelia, Ananassa, 
Billbergia, Pitcairnia, Tillandsia. They are natives 
of moist warm climates. The common pine-apple 
i^A. saliva) receives its English name from the 
circumstance of its fruit being covered on all sides 
with small triangular scales, resembling the cone 
of a pine-tree. What is called the fruit is, in fact, 
the fruits of the same spike cohering into one 
mass, by means of their succulent bracts. 

The order has several important uses. Several 
of the species are esteemed for their showy blos- 
soms ; and the tough leaf-fibres of many produce 
excellent cordage. Some of the Tillandsias, which 
hang their black thread-like festoons from the 
trees of Brazil, are collected and used for stuff- 
ing mattresses, saddles, &c. Most of the genera 
yield a fine aromatic odour ; and from their habit 
of retaining water in the sheathing axes of their 
leaves, are said to be specially grateful to the 
traveller in the regions where they abound. 

LiLlACE.'E. — A very extensive, and, to the florist, 
one of the most important of the natural orders. 
Taking the common white lily as the type, there 
is a great resemblance in all the Lilyworts, not 
only in their habits and forms, but also in their 
essential characters ; but botanists have somewhat 
perplexed themselves by subdivisions founded upon 
minute differences. It must be confessed that the 
limits of the order are not very clearly defined. 
The plants may be gener- 
ally characterised as having 
usually scaly or tunicated 
bulbs ; and leaves not arti- 
culated with the stem, either 
sessile or with a narrow 
petiole. In some of the I 
genera, the flowers are erect 
and single, as in the tulip ; 
in others, they are erect, but 
in umbels, as in the orange- 
lily ; and in others they are 
in racemes and drooping, as 
in yucca ; or single and drooping, as in the fritil- 
lary ; or with the segments curved back, as in the 
martagon lily. Perianth, coloured, regular, and 
divided into six segments, occasionally tubular ; 
stamens, six, inserted into the segments of the peri- 
anth ; anthers, opening inwards ; ovary, superior, 
three-celled, and many-seeded ; style, one ; stigma, 
simple or three-lobed ; fruit, either a three-celled, 
three-valved capsule, or fleshy, and then occasion- 
ally tripartite. The seeds of the Asphodeleas have 
a black, crustaceous, brittle testa ; in the Tulipeae 
and Hemerocallideas the testa is brown and 
spongy. 
The following plants may be mentioned as illus- 




Liliaceous Flower. 



tratiye of the principal genera : Lilium chalce- 
dontatm, the scarlet martagon lily, supposed to be 
the Krinon, or lily of the field of the New Testa- 
ment ; Tulipa sylvestris, the wild yellow tulip ; 
Alliutn cepa, the onion ; Fritillaria Meleagris, 
the fritillary ; Hyacinthus orientalis, the garden 
hyacinth ; Endymion nutans^ the bluebell ; Aspar- 
agus officinalis, the garden asparagus ; Muscari 
racemosa, the grape hyacinth ; Erythronium dens- 
canis, the dog's-tooth violet ; Phormium tenax, 
the New Zealand flax ; Aloe, the aloe ; Hemero- 
callis, the day-lily ; Scilla, squills ; Asphodelus, 
king's spear ; Ornithogalum umbellatiiin, the star 
of Bethlehem or doves' dung of Scripture. The 
Lilyworts are found in every quarter of the globe, 
being more abundant, however, in temperate than 
in tropical climates, where they exist chiefly in 
arborescent forms. 

The properties of the order present considerable 
differences. All the Asphodeleee contain a bitter 
stimulant principle, and have a viscid juice, as is 
exemplified by the onion, garlic, leek, and chives. 
The roots of some are purgative, as the aloe ; 
while those of several lihes are eaten in Siberia. 
Gum-dragon is the styptic juice of Dracana 
Draco, which yields a gum called Dragons' Blood ; 
New Zealand flax is the tough fibre of the leaf of 
Phormium tenax; squills is a well-known demul- 
cent ; and the succulent suckers of asparagus are 
largely eaten as a vegetable. Xanthorhoea hastile 
and arborea are the grass-trees of New South Wales, 
which yield a resin used by the natives for fixing 
wooden handles to stone hatchets or hammers. 

Palmace^. — An important order of arborescent 
plants, with lofty, usually unbranched trunks, 
bearing a tuft of leaves on 
the summit. The leaves are 
large, pinnate or fan-shaped ; 
flowers, small, arranged on 
a simple or branched spadix, 
which is inclosed in a one 
or many valved spathe ; 
florets, bisexual or polyga- 
mous ; perianth, six-parted, 
and persistent, its parts in a 
double row — the three outer 
segments often smaller, the 
three inner sometimes deeply 
connate ; stamens inserted 
into the base of the perianth, 
usually six, seldom three, and in a few polygamous 
species, indefinite ; ovary, one or three celled, or 
deeply three-lobed ; ovules, three, rarely one ; 
fruit, a nut, drupe, or berry ; albumen, cartilagin- 
ous or hard, often ruminate, with a central cavity. 

The principal genera are — Cocos, the coco-nut ; 
Phcenix, the date-palm ; Sagus, the sago-palm ; 
Calamus, the rattan canes ; Areca, the betel-nut ; 
Borassus, the Palmyra-palm ; Ceroxylon, the wax- 
palm ; Elais, the oil-palm ; Lodoicca, the double 
coco-nut ; Phytelephas, the vegetable ivory-palm ; 
and Hypha:ne, the doom-palm of Eg>'pt. They 
are strictly inhabitants of the tropics, to the natives 
of which they are undoubtedly the most useful 
order of vegetation. 

The properties of the Palms arc numerous and 
varied — wine, oil, wax, flour, sugar, salt, thread, 
utensils, habitations, and food, being obtained 
from numerous species. Coir, which is worked 
into mats and cordage, is the dry fibrous pericarp 
of the coco-nut. .^ 

109 




Palm. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




BUTOMACEiE. — A small order of aquatic plants, 
having very cellular leaves, furnished with parallel 
veins, and handsome umbellate flowers of a purple 
or yellow colour. Calyx, three-sepaled, usually 
herbaceous ; corolla, three-petaled and coloured ; 
stamens, definite or indefinite ; ovaries, superior, 
three, six, or more, either distinct or united ; 
foUicles, many-seeded ; seeds, minute, attached to 
the whole inner surface of the fruit. 

The genera are — Butomus, Lintnocharis, and 
Hydrochleis, which abound respectively in the 
marshes of Europe, South America, and the East 
Indies. B. utnbella- 
tus, the flowering rush, 
an enneandrous plant, 
is found in ditches 
and by river-sides in 
some parts of Britain, 
growing from two to 
three feet high, with 
sword-shaped leaves, 
and umbels of rose or 
purplish white flowers. 
Lintnocharis Plumieri, 
a native of Brazil, has 
yellow flowers, and the 
apex of each leaf is fur- 
Flowering Rush, nished with a curious 
pore, apparently for the 
discharge of the superabundant moisture which 
constantly distils from the plant 

The order is said to possess acrid and bitter 
properties ; and most of the species yield a milky 
juice. 

GLUMIFER^. 

The plants in the section Glumiferas of the 
Monocotyledons are destitute of a regular calyx 
and corolla, having instead 
green or brown scales to 
cover the stamens and 
pistil. The glume or chaff 
of the oat (see fig.) is a 
familiar example of this 
kind of envelope. The 
Sedges (CvpERACEiE) and 
the Grasses (Gramine^) 
are the only orders ranking 
We can merely glance at 
the latter — noticing a few of the genera which lie 
within the inspection of every one. 

Gramine^. — One of the most important and 
valuable, as it is^ one of the most extensive, of 
the natural orders. It comprehends 4000 known 
species, including the common grasses of our 
pastures, the cereals — wheat, barley, rye, oats, and 
maize ; the sugar-cane, rice, &c. Their roots are 
fibrous or bulbous ; their culms or stems cylindrical 
and hollow, except at the joints, where they become 
solid, the whole culm generally covered with a sili- 
cious coating ; leaves alternate, and though sheath- 
ing the stem, not united round it ; flowers in spike- 
lets, and arranged in a spiked, racemed, or panicled 
manner. The characters of the fructification are 
— flowers, either solitary or arranged in spikes, 
usually hermaphrodite, sometimes monoecious or 
polygamous, consisting of imbricated bracts, of 
which the most exterior are called glumes, the 
inferior immediately inclosing the stamens, palecs, 
and the innermost at the base of the ovarium, 
scales : glumes, usually two, alternate, sometimes 

119 




under this sub-class. 



single, often unequal ; paleae, two, alternate, i 
lower or exterior simple, the upper or interior 
supposed to be composed of two united by their 
contiguous margins, and usually with two keels ; 
scales, two or three, sometimes wanting ; stamens, 
hypogynous ; anthers, versatile ; pericarp, usually 
undistinguishable from the seed, membranous ; 
albumen, farinaceous. 

The Grasses are scattered all over the globe, 
and are the most directly useful of all vegetation 
both to man and to the lower animals. The 
following well-known plants may be taken as illus- 
trative of the order : Triticuvi vulgare, common 
wheat, which, accord- 
ing to the experiments 
of Fabre, appears to 
have originated from 
a small weedy grass 
{JEgilops ovala), not 
uncommon on the 
shores of the Mediter- 
ranean. Hordeum dis- 
tichunt, common two- 
rowed barley ; Secale 
cereals, rye ; Avena 
saliva, common oat ; 
Zea mays, maize or 
Indian corn ; Sac- 
charum officinarum, 
the sugar-cane ; Oryza 
saliva, rice ; Bambusa 
arundinacea, the bam- 
boo ; Phleum pratense, 
cat's-tail or Timothy 
grass ; Anthoxanthum 



A 

lor 1 




Sugar-cane. 



odoraliim, sweet-scented 
vernal grass ; Dactylis glomerala, cock's-foot 
grass ; D. ccespilosa, the tussac-grass ; Andropogon 
Schoenanlhus, the lemon-grass ; Gynerium argen- 
leum, the Pampas-grass ; Phalaris canariensis, 
the canary-seed ; Sorgham species, the guinea- 
corn ; Festuca pratensis, meadow-fescue ; Lolitim. 
perenne, rye-grass ; Briza media, quaking-grass ; 
A hpecurus pratensis, meadow fox-tail grass ; and 
Holcus lanatiis, woolly soft grass. The cereal 
grains are plants of very ancient cultivation, and 
not being now found in a wild state, the origin of 
some of them is doubtful. Though allied in many 
respects to the Sedges, the Grasses are readily 
distinguished by their round hollow-jointed stems, 
and leaves that sheathe, but do not completely 
surround, the stem like a tube. The Grasses 
have a thin silicious coating on their stems, which 
seems intended to furnish them with greater 
strength and durability than could have been pro- 
cured by simple ligneous fibre. 



ACROGENOUS OR ACOTYLEDONOUS 
(FLOWERLESS) PLANTS. 

This class of vegetation is readily distinguished 
by none of its members bearing proper flowers — 
hence the terms Cryplogamia and Flowerless. 
The higher forms exhibit a peculiar kind of tissue, 
called scalariform vessels, as well as spiral vessels ; 
but the lower forms consist of cellular tissue only. 
They exhibit very different degrees of organisa- 
tion — the highest {ferns) having both stems and 
leaves {fronds), and the lowest consisting of simple- 
jointed threads, or even mere individual cells. 
Between these two extremes there are various 



SYSTEMATIC BOTANY. 



conditions of stem and leaf— the two most fre- 
quently graduating into each other, and forming 
neither true leaf nor stem, but thin expansions, 
termed thalli. Cryptogamic plants do not origin- 
ate from seeds, containing embryos, like the 
flowering-plants, but are reproduced by means of 
spores — bodies which in their simplest form con- 
sist of a single cell, but which are very varied in 
morphological character in different families. There 
are two sub-classes. 

§ 1. ACROGENjE. 

•Filices — Ferns. *Equisetacese — Horse-tails. 

•Lycopodiaceac — Club-mosses, *Musci — Mosses. 
*Marsileace2e — Pillworts. *HepaticK — Liverworts. 

FiLjCES. — In this order the different parts of 
the plant spring from a rhizome, or root-stock ; 
the elegant fronds or leaves being either separate 
and independent, or uniting by their stalks so as 
to form a sort of trunk, as in the tree-ferns. The 
fronds are furnished with forked veins, and are 
usually pinnatifid, and more or less compound ; 
sometimes nearly simple and entire ; in their ver- 
nation they are circinnate — that is, they unroll 
from the stem outwards in the form of a crosier. 
The reproductive organs appear on the mature 
plant in the form of sort, or brown membranous- 
looking spots, usually either upon the backs of the 
fronds, or on their margins. These sori either lie 
under a small shield-like indusium, or they are 
naked ; or they are arranged along the margin 
of the leaf, which curls over them, and supplies 
the place of the indusium. Each sorus consists 
of a number of brownish bodies, called thecce, or 
sporangia, each being in reality a case containing 
a number of minute spores, which are the true 
reproductive bodies. (For details of the develop- 
ment of these spores into plants, see Vegetable 
Physiology, page 75.) 

The Ferns are divided into the following sub- 
orders : I. POLYPODIACE^ ; sporangia in vari- 
ously shaped sori on the back or margin of the 
frond, each having an elastic ring or rachis (verti- 
cal and incomplete, or horizontal and complete), 
by means of which the ripe sporangium is torn so 
as to set the contained spores free. 2. OSMUN- 
DACEiE ; sporangia on a transformed contracted 
frond, with a terminal or dorsal ring more or less 
complete, reticulated, and opening vertically. 3. 
OPHlOGLOSSACEiE ; sporangia in spikes, sessile 
on a contracted frond, exannulate, two-valved 
(vernation of frond straight). 4. DANiEACEiE ; 
sporangia dorsal in masses, exannulate, splitting 
irregularly by a central cleft. The first sub-order 
is illustrated by the following 
genera : Polypodium, the poly- 
pody, which has naked sori ; 
Lastrea, the shield-fern; Cysto- 
pteris, the bladder-fern ; Asple- 
niuni, spleen-wort ; Pteris, the 
common brake ; Athyrium, to 
which belongs the lady-fern of 
our woods ; Adiatiium, maiden- 
hair ; and Scolopendriutn, hart's- 
tongue, the frond of which is 
tongue-shaped and simple. The 
second sub-order is represented 
by Osmunda, the Royal fern ; 
Anemidictyon, and Lygodium, 
the climbing-fern. The third sub-order contains 




Tree-fern. 



Botrychium, the grape-fem or moon-wort; and 

Ophiglossum, the adder's-tongue ; and the fourth 
sub-order, a few exotic genera. The Filices are 
widely distributed, delighting in humid soil and 
shady situations — some growing on trees. 

The fronds of the family generally contain an 
astringent mucilage, and are thus considered as 
pectoral; the roots of some have recently been 
used successfully as anthelmintics and purgatives ; 
and Aspidium fragrans has been employed as a 
substitute for tea. The young leaves and rhizomes 
of some New Zealand species are edible ; and the 
fronds of the common brake, when burned, yield 
a considerable quantity of alkali. 

Lycopodiacea (Club-mosses), Efuiseia/:ece{Horsc- 
tails), and Marsileacece (Pillworts), are usually 
classed as Fern Allies. They display consider- 
able variety of structure, and will well repay care- 
ful study. 

MusCL — ^The Mosses present many points of 
interest. They are minute plants, with erect or 
creeping stems and small leaves, all their tissues 
cellular. At certain seasons, little flower-like 
heads are produced, some containing antheridia 
(so named from their resemblance to anthers), 
and others less conspicuous, consisting of pistil- 
lidia, which represent the female parts. At matu- 
rity, each antheridium opens at the apex, and 
emits a granular gelatinous mass ; this consists 
of minute spermatozoa, which find their way into, 
and impregnate the pistillidia, and thus give rise 
to the development of the latter into an urn- 
shaped theca or spore-case, containing spores 
capable of germinating into new plants. 

Mosses grow usually in shady situations, and 
are abundant in moist, temperate countries. They 
are divided into three sub-orders — Andreaeaceae, 
Sphagnaceae, and Bryaceae. The first is illustrated 
by the split-mosses {Andrecea), which are common 
on the Scottish hills ; of the second, Spltagnum, 
bog-mosses is the only genus ; while the third 
embraces the genera Bryum and Hypnum, and 
most other British mosses. 



§ 2. THALLOGENiE. 

The orders under the Thallogenous sub-class 
of Cryptogams are : 



*Lichenes — Lichens. 
•Fungi — Mushrooms. 



•Algae — Sea-weeds. 
'Ctuuaceae — Charas. 



Lichenes. — Lichens form not the least inter- 
esting section of the Cryptogamia, and their value 
on the score of utility is by no means unim- 
portant. They are familiar objects to all in the 
form of apparent discolorations and incrustations 
on old walls and rocks ; but some of them hang 
in festoons from the branches of trees (Usma, 
Alectoria), while others {Peltided) spread their 
thalli among mosses and herbage in shaded situ- 
ations. They grow slowly, and attain an extreme 
age, as some of those growing on the primitive 
rocks of our highest mountain-ranges must be. 
'The hoary Usneas, Ramalinas, and Physcias, 
like the gray beard of an old man, silently but 
eloquently proclaim time's ravages, and illustrate 
the constant succession of life upon death, growth 
upon decay, which is going on around us.' In 
their reproductive organs, they approach the 
Fungi, but are well distinguished by the presence 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



I 



in their tissue of gonidia containing chlorophyl, 
which are capable of originating new plants. 

The Lichens yield valuable dyes. Orchil, a red 
dye, supposed to have supplied the purple of 
ancient Tyre, is produced by Roccella tinctoria, a 
Southern European species which was discovered 
in the Cumbray Islands, in the west of Scotland, 
by Professor Balfour in 1855. Cladonia rangifc- 
rina is the Reindeer Moss, an important forage- 
plant in Lapland. Species of Gyrophora {Tripe 
de Roche) are edible, and furnished Franklin and 
his companions with food for many weeks in arctic 
regions. Cetraria islandica, the Iceland moss, 
contains starch and a bitter principle. Lecanora 
tai'tarea, the rock-moss, supplies the cudbear dye ; 
and Parnulia parietina yields a yellow dye. 

Fungi. — The Fungi, or Mushroom family, 
which are among the lowest forms of vegetation, 
are extremely diversified in their size, shape, 
colour, and consistence. The common field- 
mushroom is one of the best known, and may be 
cited as a type of the family ; but the puff-ball, 
truffle, moril, as well as the mould on cheese and 
stale bread, the mildew on trees, the rust on corn, 
the substance called dry-rot, and many other 
minute appearances of a similar nature, are all 
fungi. In the field-mushroom {Agaricus campes- 
iris), the plant consists first of some filamentous 
filaments or spawn, which look like roots, then 
the stipe or stalk, surmounted by the pileus or 
cup. 'When the mushroom first appears, the 
stalk is covered by a thin membrane, called the 
veil, which unites the cup to the lower part ; but 
as the mushroom grows, this veil is rent asunder, 
and it either entirely disappears, or only a small 
portion of it remains round the stalk, which is 
called the annulus or ring. Under the cup are 
gills or lamellze, which are of a dark reddish 
brown ; and attached to these are the thecse, con- 
taining the spores.' Many — as the moulds, &c. — 
are mere microscopic jointed filaments, or fila- 
ments surmounted by little ball-like receptacles 
which contain the sporules, or are mere spherical 
or filamentous cells, which increase with astonish- 
ing rapidity, each cell containing a number of 
undeveloped ones. 

Among the more familiar genera are — Agaricus, 
the mushroom ; Tuber, the truffle ; Morchella, the 
morel ; Lycoperdon, the puff-ball ; Puccinia, the 
mildew ; Clavaria, the yellow meadow fungus ; 
Podisoma, the jelly-looking masses often found on 
juniper and savin bushes ; and Ttiberailaria, the 
small, red, pimple-like fungus found on rotten 
sticks and trunks of trees. The Fungi are scat- 
tered everywhere — springing from the ground, yet 
without roots ; under the ground, as the truffle ; 
on all decaying organic substances ; and even on 
living animals. What is called yeast is a spheri- 
cal-celled fungus, having a nucleated develop- 
ment. 

The plants of this order are not more diversified 
in form than in properties. Some are wholesome 
and palatable — as the mushroom, moril, truffle, 
&c. ; others, similar to these in appearance, are 
deadly poisons. Many of the minuter fungi — as 
moulds, smuts, rusts, &c. — are noxious to the 
112 



human system. Ergot forms a powerful and 
dangerous medicine. German tinder is prepared 
from a species of puff-ball, which, after being 
dried, is impregnated with nitre. The Siberian 
fungus {Amanita) is used to induce intoxication. 
The vinegar plant is one of the most singular 
forms of fungi ; it is an abnormal state of Penicil- 
lium glaucutn developed in saccharine fluid, which 
it has the property of converting into vinegar 
suited for table use. 

AlG/E. — The Algae form a highly interesting 
family of plants, and are specially important to the 
physiologist, for it is in these that the phenomena 
of growth and reproduction are most successfully 
studied. This order — which has been wisely split 
up into several orders, concerning which our space 
will not permit of full details — embraces the very 
simplest forms of vegetation, as well as many 
having a complicated structure. The Algas are 
not confined to the sea ; many occur in fresh 
water and on the dry land. They are classified 

as follows : I. MELANOSPERMEiE Or FUCACE^ ; 

brown-coloured sea-weeds. 2. RhodospermEvE 
or CERAMlNACEiE ; rose-coloured sea-weeds. 3. 
CHLOROSPERMEiE or CoNFERVACE^E ; green- 
coloured sea and fresh-water weeds. 4. Diato- 
MACE2E, Brittleworts ; unicellular, in the form of 
frustules, usually coated with silica, and contain- 
ing brown, rarely green, contents. 5. Desmidiete ; 
unicellular, without silica, containing always green 
cell-contents. The first contains many of our 
large species of common sea-weeds ; the second, 
those beautiful kinds so highly prized for albums ; 
the third, those green filamentous species so 
common in stagnant waters, some of which fill up 
lakes with their interlaced masses of filaments ; 
the fourth, those minute silicious bodies found in 
such amazing quantities in all parts of the world ; 
and the fifth, the analogous non-silicious species, 
which display perhaps the most beautifully sym- 
metrical forms of the vegetable kingdom. 



Such, according to our limits, is an outline of 
the Natural System of Botany ; which, though 
as yet not fully developed, is more interesting 
and instructive than any artificial method, how- 
ever elaborate and complete. Undeveloped as we 
must admit it to be, harsh and difficult as much 
of its nomenclature is, unnecessarily multiplied 
and complicated as its orders and tribes really 
have been, it has still the germs of truth and 
nature within it, and only requires a cordial and 
patient elaboration, on the simple principles of its 
great founder, to render it what it professes to be 
— an exposition of the system upon which Nature 
has proceeded in the creation of the Vegetable 
Kingdom. Our brief synopsis can at most but 
convey a very general notion of vegetable life and 
relationship, and only introduce the student to the 
technical phraseology and mode of procedure : for 
further acquaintance with the subject, we cannot 
refer to more accessible sources than the excellent 
works published by Professor Asa Gray, Professor 
Lindley, and Professor Balfour. 



HUMAN PHYSIOLOGY. 



HUMAN PHYSIOLOGY is the science which 
treats of the functions of the body and the 
manner in which these are performed. By a 
function we mean the action performed by any 
part of the body. For example, one of the 
functions of the liver is to secrete bile, while 
that of the stomach is to digest food. It is 
the object of the present paper to describe as 
briefly as is compatible with clearness the most 
important of these functions. The functions of 
the human body may be conveniently classified 
into three great divisions : i. The Function of 
Nutrition, or the nourishment of every part of the 
body, so as to enable each part to perform its 
special function ; 2. The Function of Innervation, or 
the actions performed by the nerves, spinal cord, 
and brain ; and 3. The Function of Reproduction, 
or the perpetuation of the species by offspring. 



I. THE FUNCTION OF NUTRITION. 

This function is a con^plex process. To keep 
up the integrity and vigour of the body, food 
must be procured, chewed or masticated, mixed 
with saliva, swallowed, digested in the stomach, the 
nutritious material absorbed by special organs in 
the bowels, called villi, and from them carried 
to various glands, where it is elaborated into 
blood. The blood is then conveyed through 
the body, giving up to the tissues what they require 
for nourishment, and carrying away materials 
resulting from their decay. Thus rendered im- 
pure, the blood must have the noxious materials 
removed. For this purpose, several organs, such 
as the lungs, the liver, the skin, the kidneys, and 
the lower bowel, are set apart. Thus the blood 
is constantly replenished with nutritious matters, 
and constantly being purified, so as to fit it for 
supplying each individual particle or cell of the 
body with exactly the material it requires. Bone 
requires earthy salts, muscle requires albumen, 
the nervous system requires fat, and so on. 

The process of nutrition is complex only in the 
higher animals. In the amoeba, a Httle animal 
which is nothing more than a mass of jelly-like 
living material, we find no trace of organs, and 
nutrition is carried on by any part of the body. 
But as we ascend in the scale of animal life, one 
organ after another is added, such as a digestive 
sac, glands for secretions to act on the food, a 
special fluid — the blood, an organ and vessels 
for circulating this fluid ; and so on, till we 
come to the higher animals, where we find great 
differences in parts, and corresponding differences 
in function. We will divide nutrition into the 
following thirteen stages, namely: 

I. FOOD, OR ALIMENT. 

A living being is always in a state of change. 
His skin gives off water, either in the form of 
8 



sweat, or as invisible vapour; his kidneys act 
similarly, the water in both cases containing salts 
and other matters in solution ; and his lungs are 
always exhaling, not only watery vapour, but the 
gas known as carbonic acid, as maybe readily shewn 
by breathing into lime-water, which soon assumes 
a milky appearance, in consequence of the forma- 
tion of carbonate of lime. Moreover, the body, 
which has an almost constant temperature of 
about 98-4° F. is always giving off heat. The 
production of heat indicates chemical changes 
in the body, accompanied by waste of material. 
If this condition of things were to go on indefi- 
nitely, the weight of the body would gradually 
diminish. To retain the body in its normal state, 
we must therefore supply it with three things — 
atmospheric air, water, and food. We have placed 
them in the order of their importance. 

Various classifications of the food of man have 
been proposed ; but the following is simple and 
practical : (i) the aqueous, (2) the albuminous, (3) 
\!as. fatty, oily, or oleaginous, (4) the saccharine, (5) 
the gelatinous, and (6) the saline groups. All our 
daily food is referable to one or more of these 
classes. The aqueous group includes not only 
water, but all fluids (except oils) used as drink, 
and it must be recollected that all our so-called 
solid foods contain a large percentage of water. 
The albuminous group (often termed the protein) 
is typified by the white of egg, and includes the 
gluten of flour, the chief constituents of flesh 
and cheese. These substances contain the four 
elements, carbon, hydrogen, oxygen, and nitro- 
gen, and also a little sulphur or phosphorus, or 
both. The albuminous foods chiefly nourish the 
muscles, but they contribute, along with fat or 
oil, to almost every tissue. The fatty group in- 
cludes all animal and vegetable fats or oils. They 
are composed of carbon (ranging from 60 to 80 
per cent.), hydrogen, and a little oxygen. The sac- 
charine (often termed the starchy or amyloid) g^oup 
contains all the varieties of sugar, starch, dex- 
trine, and gum ; like the preceding group, they are 
composed solely of carbon, hydrogen, and oxygen. 
Both the fats and sugars belong to the group 
termed by chemists hydrocarbons, because they 
contain carbon or charcoal, and oxygen and hydro- 
gen, in the proportions, or nearly in the propor- 
tions, necessary to form water. They contribute 
chiefly to the adipose or fatty tissue of the body. 
The gelatinous group is represented by cow-heel, 
isinglass, and such-like substances, yielding jellies 
and soups that stiffen on cooling ; while the saline 
group includes mineral matters, especially common 
salt, and phosphates of the alkalies, and of lime, 
&c. The saline or mineral matters form bone, 
tooth, &c. and they are found in variable propor- 
tions in almost every fluid and solid in the body. 
It must be remembered, however, that a mixture 
of all of these constituents of food is essential to 
the formation of a nutritious diet, and, moreover, 
that there must always be a certain amount 
of sapidity or. flavour in the food. We should 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



I 



turn with disgust from a mess consisting of these 
constituents, even in proper proportions, if it were 
not properly cooked. The best example of a 
natural food is milk. It contains water, albumen 
in the form of caseine or cheese, fat in the form 
of butter, sugar, and various salts. Hence it is 
nature's food for all young animals of the mam- 
malian group. 

A daily amount of food varying from 33 to 35 
ounces of dry food is sufficient to maintain the 
health of an adult man, not engaged in active 
labour, and of this a fourth or fifth part should be 
animal food ; but in special cases much more or 
less may be taken with advantage. The arrange- 
ment and form of the teeth in man indicate that 
he should live on a mixed diet of animal and 
vegetable food ; though, no doubt, there are ex- 
amples on record of individuals who have lived in 
good health for many years entirely on either 
animal or vegetable food. By mixing these in 
proper portions, we are nourished on a smaller 
bulk of food than if we lived on either one or the 
other. 



2. MASTICATION. 

Mastication is effected in the cavity of the 
mouth by means of the teeth, which fit into sockets 
in the upper and lower jaw-bones. The upper jaw 
is immovable, or only movable with the entire 
head ; but the lower jaw, with its teeth, is capable 
of moving upwards, downwards, backwards, for- 
wards, and laterally, by means of the powerful 
muscles of mastication. It is by the varied move- 
ments of the lower teeth against the upper, through 
the action of these muscles, that food is broken 
down or masticated. In the adult there are 32 
teeth, 16 in each jaw, and 8 on each side. There 
are from before backwards, beginning in the 
middle line of the jaw, 2 incisors or cutting 
teeth on each side ; i canine or eye-tooth, for 
seizing ; 2 premolars or bicuspids, for tearing ; 
and 3 molars or grinders, for crushing and break- 
ing up the food. The body and greater bulk of 
each tooth consists of a substance called dentine, 
composed of branching tubes ; the top or crown is 
covered by a cap of enamel, a very hard substance, 
made of small hexagonal prisms ; and the fang or 
root is protected by a layer of a material resembling 
bone, called crusta petrosa, or cement. In the 
centre of each tooth there is a cavity containing 
a pulpy matter, in which are nerves and blood- 
vessels. 



3. INSALIVATION. 

Insalivation is effected by the admixture of the 
secretions of the three pairs of salivary glands (the 
parotids, the sub-maxillaries, and the sub-linguals), 
and of the mucus secreted by numerous small 
glands beneath the lining of the cheeks, gums, and 
tongue, called buccal glands, with the triturated 
food. The common saliva formed by the com- 
bined secretion of these various secreting organs, 
is a colourless, slightly turbid, viscid, inodorous, 
and tasteless fluid. In the normal state, its reac- 
tion is alkaline. Saliva does not contain more 
than five or six parts of solid constituents to 
995 or 994 .parts of water. The daily quantity 
of saliva secreted by an adult man is estimated 
at about 48 ounces, but the activity of the 

lU 



salivary glands is dependent upon various in- 
fluences and conditions. Thus, movement of 
the lower jaw, as in masticating, speaking, or 
singing, increases the secretion — acrid and 
aromatic substances and hard dry food also 
increase it. It is also under the influence of 
mental emotions and desires, through the nervous 
system, for the sight of a feast or tempting dish 
may make one's ' mouth water.' 

The uses of the saliva in reference to digestion 
are partly mechanical and partly chemical. The 
chemical use of the saliva is to convert the starchy 
portions of the food into grape-sugar, and thus 
to promote its absorption. It also assists in 
speech and swallowing. The public speaker can- 
not articulate when his mouth becomes dry, and 
we cannot swallow a perfectly dry powder. 

4. DEGLUTITION. 

Deglutition is the act by which the food is 
transferred from the mouth to the stomach. The 
mouth leads into a cavity called the pharynx. 
Between it and the mouth is the pendulous or soft 
palate, which is a movable muscular partition 
that separates the two cavities during mastication. 
As soon, however, as the latter act is accomplished, 




Fig. I. — Human Alimentary Canal : 

a, oesophagus : b, stomach ; c, cardiac orifice ; d, pylorus ; e, small 
intestine ; /, biliary duct ; g, pancreatic duct ; h, ascending 
colon ; i, transverse colon ; /, descending colon ; k, rectum. 

and the bolus is pressed backwards by the tongue, 
the soft palate is drawn upwards and backwards, 
so as to prevent the food passing into the nose. 
The opening of the windpipe is closed by a lid 
called the epiglottis. The bolus or pellet of food 
having arrived near the oesophagus or gullet 
(which is continuous inferiorly and posteriorly 



HUMAN PHYSIOLOGY. 



^vith the pharynx), is driven into it by the action 
of certain muscles, which almost surround the 
pharynx, and are termed its constrictor muscles. 
All voluntary action ceases as soon as the food is 
pressed backwards by the tongue into the pharynx. 
It is impossible to recall the pellet, and it is 
necessarily carried on (without even our cogni- 
sance) into the stomach. This involuntary mech- 
anism is called a reflex action. All reflex 
actions require a stimulus to call the parts into 
action. The stimulus in this case is the contact 
of the food with the back of the tongue and 
throat. It will be found on experiment that the 
reader cannot perform the action of swallowing if 
nothing, not even saliva, is in his mouth. 

5. DIGESTION IN THE STOMACH. 

The whole of the alimentary canal below the 
diaphragm, or muscular partition which sepa- 
rates the cavity of the chest from that of the 
abdomen or belly, possesses the following points 
in common, in relation to structure. The stomach, 
the small intestine, and the large intestine, are all 
lined by mucous membrane, have a muscular coat 
consisting of two sets of distinct fibres — namely, 
circular fibres which surround the tube or viscus 
after the manner of a series of rings, and longi- 
tudinal fibres running in the same direction as the 
intestine itself — and are invested with a smooth, 
glossy, serous membrane, which, while it retains 
the viscera in their proper position, also permits 
their necessary movement with a minimum of 
friction. 

The human stomach is an elongated curved 
pouch, lying immediately below the diaphragm. 
It is very dilatable and contractile, and its func- 
tion is to retain the food until it is duly acted 
upon and dissolved by the gastric juice, which is 
secreted by glands lying in its inner coat, and 
then to transmit it, in a semi-fluid state, into the 
first part of the small intestine, called the duo- 
denum. Its average capacity is about five 
pints. 

The mucous membrane, or lining coat of the 
stomach, is thick and soft, and lies in irregular 
folds, in consequence of the contraction of the 
muscular coat, unless when the organ is distended 
with food. On opening the stomach, and stretch- 
ing it so as to remove the appearance of folds, we 
perceive numerous very shallow pits or depressions. 
The rest of the thickness is chiefly made up of 
minute tubes, running vertically towards the surface 
of the stomach, and secreting the gastric juice from 
the blood in the capillaries or minute blood-vessels 
which abound in the mucous membrane. These 
tubes are lined half-way down with epithelial 
cells, and the bottom is during digestion filled 
with molecular matter and a few cells. Other 
tubular glands are also found in the stomach, 
which are believed to secrete mucus. 

When food is introduced into the stomach, it 
is subjected to three actions — first, to heat, the 
temperature of the stomach being, during diges- 
tion, about 99° F.) ; second, to a slow movement 
round and round, so as to bring the food into con- 
tact with the lining ; and, third, to the chemical 
action of a special fluid— the gastric juice. 

The food on entering the stomach first passes 
into the cardiac end, thence along the greater 
curvature from left to right to the pyloric end, and 



from thence along the lesser curvature from rieht 
to left. *" 

The changes in the mucous membrane are — 
The inner surface of the healthy fasting stomach 
is of a paler pink than after the introduction of 
food, which causes the exudation of a pure, colour- 
less, viscid fluid, having a well-marked acid reac- 
tion. This fluid, which is the gastric juice, collects 
in drops, which trickle down the walls, and mix 
with the food. Its two essential elements are— i. 
A free acid, which in some cases seems to be 
hydrochloric alone, and in others a mixture of 
hydrochloric and lactic acids ; and 2. An organic 
matter called pepsine, which is highly nitrogenous, 
and allied to the albuminates. 

The uses of this fluid are not only to dissolve but 
also to modify the nitrogenous elements of the food 
(such as albumen, fibrine, caseine, and, in short, 
all animal food except fat, and the albuminous 
principles of vegetable food), converting them into 
new substances, termed peptones, which, although 
they coincide in their chemical composition, and 
in many of their physical properties, with the 
substances from which they are derived, differ 
essentially from them in their more ready 
solubility in water, and in various chemical 
relations. 

The gastric juice exerts no action on the 
fats and the carbon-hydrates (sugar, starch). If 
the fats or starches are in cells, the walls of which 
are formed of albumen, the walls are dissolved, 
and the contents set free. 

The process of gastric digestion is slow. Accord- 
ing to Beaumont's researches on Alexis St Martin, 
a man who had an injury which left a permanent 
opening into his stomach, guarded by a little valve 
of mucous membrane, the mean time required for 
the digestion of ordinary animal food, such as 
butcher-meat, fowl, and game, was from two hours 
and three-quarters to four hours. 

What becomes of the matters that are thor- 
oughly dissolved in the stomach ? The albumin- 
ates, &c. which are converted into f)eptones, are 
for the most part taken up by the blood-vessels, 
and by another set of vessels called the lacteals. 
The rapidity with which aqueous solutions of 
iodine of potassium, the alkaline carbonates, 
lactates, citrates, &c. pass into the blood, and 
thence into the urine, saliva, &c. shews that the 
absorption of fluids must take place very- shortly 
after they are swallowed ; and there is little doubt 
that the blood-vessels (capillaries) of the stomach 
constitute the principal channel through which 
they pass out of the intestinal tract into the 
blood. 

There can be no doubt that the stomach is 
admirably adapted for the digestion of the food 
introduced into it, because it has been shewn by 
numerous exp>eriments that digestion will go on 
in gastric juice out of the stomach, but that it 
requires three or four times longer a period than 
when performed by the stomach itself. In the 
stomach, in most individuals, rice and tripe are 
digested in one hour; eggs, salmon, and venison 
in one and a half hours; tapioca, liver, fish, in 
two hours ; lamb, pork, and turkey in two and a 
half hours ; beef, mutton, and fowl, three and a 
half hours; and veal in four hours. There .ire, 
however, considerable differences in various indi- 
viduals, or even in the same individual at different 

times. 

lU 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



6. DIGESTION IN THE BOWELS. 

After the food, by digestion in the stomach, has 
been converted into a semi-fluid mass called the 
chyme {chymos, juice), it passes into the intestine. 
The length of the human intestine is usually 
about twenty-five feet. As a general rule it may 
be stated that the intestines of herbivora are much 
longer than those of carnivora. This is due to the 
nature of the food. In those animals, such as the 
ox, which live on a food very different, physically 
and chemically, from the tissues of the individual, 
a complicated digestive apparatus and a long 
intestinal tube will be found ; whereas those 
which live on food readily converted into their 
own tissues (such as a weasel, which preys on 
the blood of other animals), have a simple 
digestive apparatus and a short tube. 

The human intestine consists of a convoluted 
tube, which, from a great change in calibre in two 
different parts, is divided into (i) the small 
intestine, and (2) the great intestine. The small 
intestine is about twenty feet in length, and is 
divided by anatomists into three portions — the duo- 
denum, jejunum, and ileum, the latter opening 
into the great intestine. The whole of this tube is 
connected with the back of the abdominal cavity by 
a thin web, called the mesentery, on which blood- 
vessels, nerves, and absorptive vessels called 
lacteals, ramify before penetrating and supplying 
the bowel. When the small intestine is sht open, 
it presents a large number of transverse folds, 
which are simply doublings of the mucous mem- 
brane, so as in little space to increase the surface 
for absorption. It has also a peculiar velvety 
appearance, which is due to the fact that it is 
covered over by innumerable small projections 
termed villi. They are more numerous in the 
upper than in the lower portions of the bowel. 
When examined by the microscope, they are 
found to be prolongations of the mucous mem- 
brane, shaped like the finger of a glove, and each is 
covered by a layer of epithelial cells. In the centre 
we find the commencement of the true absorbent 
vessel, called a lacteal, and surrounding it a 
network of vessels of very minute size. The viUi in 
the smaU intestine are to a certain extent compar- 
able to the delicate rootlets of a plant. The latter 
absorb moisture and soluble nutriment from the 
soil, while the former are bathed in a nutritious 
fluid, the chyme, and absorb readily fluids by the 
blood-vessels, and fatty matters by the lacteals. 
We find also scattered in large numbers over the 
mucous membrane, minute tubular glands called 
Lieberkiihnian glands, after the anatomist Lieber- 
kiihn, who first described them. In the upper 
part of tha duodenum, there are a few glands, like 
small clusters of grapes, called Brunner's glands, 
the function of which is unknown. 

The great intestine, about five or six feet in 
length, is so termed because it is so much wider 
than the smaller one. It is also divided into 
three parts : the ccecum, which is a wide pouch, 
often of great size in herbivorous animals, and 
into which the small intestine opens, the entrance 
being guarded by a valve ; the colon, which forms 
the greater part of the large intestine; and the 
rectum, which is situated entirely in the pelvis, 
and terminates in the anus. The great resembles 
the small intestine in general respects, 

116 



There is abundant evidence that the function of 
the villi is connected with absorption, and mainly 
with the absorption of fatty matters. i. The 
villi exist only in the small intestine where the 
absorption of food goes on. 2. They are turgid, 
enlarged, and opaque during the process of 
digestion and absorption, and small and shrunken 
in animals that have been kept fasting for some 
time before death. 

The function of the muscular coats is to propel 
the food along the bowel. This they perform by 
alternate contractions and relaxations, and thus a 
wave-like motion is produced. This motion may 
be readily seen in the intestines of an animal 
recently killed, and is termed a peristaltic 
action. 

When the food, reduced to a pulpy mass in the 
stomach, termed chyme, passes into the duodenum, 
it is mixed with three fluids : i, the bile; 2, the 
pancreatic juice ; and 3, the intestinal juice. 

The bile is an alkaline fluid secreted by the liver, 
and, after having been collected in the gall-bladder, 
finds its way into the upper part of the small intes- 
tine by a duct, which usually unites with that 
of the pancreas, and opens by a common orifice. 
As it flows from the liver, the bile is a thin 
greenish-yellow fluid, sometimes olive-brown ; but 
when acted on by the gastric juice, it acquires a 
distinctly yellow or green hue, hence the appear- 
ance of vomited bile. Its main use seems to be 
•to promote the digestion of fatty matters, and it 
accomplishes this end by a peculiar physical action 
both on the fats and on the intestinal walls, disin- 
tegrating the former, and impressing on the latter 
(by moistening the villi) a peculiar condition which 
facilitates the absorption of fatty matters. The 
bile separates nutritious matters from those which 
are non-nutritious, while it stimulates the mus- 
cular movements of the bowels and arrests putre- 
faction in the faeces. 

The pancreatic juice is secreted by a long, 
narrow, flattened gland called the pancreas, or 
sweetbread, which lies deeply in the cavity of the 
abdomen, immediately behind the stomach. It 
is a lobulated or racemose gland, consisting of an 
immense number of small pouches grouped round 
the extremities of small ducts. These ducts unite 
with others, becoming larger and larger, until the 
great duct of the gland is formed. 

The .secretion is a colourless, clear, somewhat 
viscid, and ropy fluid, devoid of any special odour, 
and exhibiting an alkaline reaction. It contains a 
peculiar principle called pancreatine. 

The function of the pancreatic juice is to emul- 
sionise the fat of the chyme, and thus promote its 
absorption. If the duct of the pancreas be tied, 
and fat be taken as food, a large amount of it will 
appear in the fasces ; and the same result has been 
seen in the human being in cases of diseased pan- 
creas. The pancreatic juice also converts any 
starchy matter, which may have escaped the 
action of the saliva, into grape-sugar. 

Of the last of the fluids poured into the intes- 
tine, the intestinal juice, we know little. It is the 
aggregate secretion of the various glands which 
occur in the walls of the smaller intestine. 
It is a colourless, or sometimes yellowish, ropy, 
viscid fluid, which is invariably alkaline. It 
seems to unite in Itself the leading properties of 
the pancreatic and gastric juices ; that is to say, 
it resembles the former in converting starch int^ 



HUMAN PHYSIOLOGY. 



sugar, and the latter, in dissolving flesh and other 
albuminous bodies. 

The line of demarcation between the small and 
large intestine is very obvious, and by the pecuHar 
arrangement of the ileo-caecal valve, which guards 
the entrance of the small into the great intestine, 
matters are allowed to pass forward with facility, 
while regurgitation is impossible. The contents 
of the large intestine differ very materially from 
those which are found in the small intestine, and 
constitute the faeces. They are more solid and 
homogeneous, and are often moulded into a defi- 
nite shape. The only essential change which the 
contents undergo in this part of their course is, 
that they increase as they pass onward in solidity, 
in consequence of the absorption of fluid from 
them by the mucous membrane. They are pro- 
pelled onwards into the rectum by the vermicular 
action which has been already described, and are 
at last expelled by a voluntary effort. 

The fasces consist partly of undigested materials 
and partly of matters which are derived from the 
mucous membrane of the great intestine. It is in 
the great intestine the chyme first acquires a faecal 
odour, which increases in intensity as the material 
passes along the bowel. This odour is not due 
simply to putrefaction, but to the presence of 
peculiar effete matters, which are thrown off by 
the Uning membrane of the bowel 

7. ABSORPTION OF NUTRITIOUS MATTER. 

As the chyme is propelled along the alimentary 
canal, the watery portion, holding various sub- 
stances in solution, is absorbed by the blood- 
vessels, while the fatty matter is taken up by the 
lacteals. It is believed that this absorptive action 
is really a physical process dependent on osmotic 
action. The whole of the nutritive material thus 
separates itself into two parts : one which passes 
directly into the blood, and the other which enters 
the lacteals, and in these becomes a milky fluid 
called the chyle. It is important to remember that 
all the blood circulating in the digestive organs 
must pass through the liver before entering the 
general circulation, and from it the cells of the 
liver select and elaborate their secretions. But 
the chyle passes into the blood indirectly. It is 
first conveyed to numerous glands in the neigh- 
bourhood of the intestines, called mesenteric 
glands. Before entering these glands it is a milky 
fluid, essentially molecular ; but after it has passed 
through the glands it is found to contain small, 
round, biconcave discs, termed chyle corpuscles, 
along with much molecular matter. The lacteal 
vessels proceeding from these glands unite with cor- 
responding sets of vessels from the lower limbs, 
called lymphatics, in a wide cavity opposite the last 
dorsal vertebra, the receptacuhtm chyli. From 
this cavity a duct, the thoracic duct, ascends 
through the thorax, receives branches from 
the left arm and left side of the head, and 
unites with the venous system at the root of the 
neck on the left side, the point of junction being 
where the left internal jugular vein unites with 
the great vein of the left arm, the left subclavian. 
The lymphatics of the rest of the body unite to 
form the right lymphatic duct, which joins the 
venous system at a corresponding point on the 
opposite side. The whole of the chyle, therefore, 
passes into the blood at the root of the neck ; from 
thence it goes through the right side of the heart 



to the lungs, where the corpuscles probably 
acquire colour, and become the coloured corpus- 
cles of the blood. 

8. SANGUIFICATION. 

By this term we mean the making of blood. In 
the lowest animals, such as in the amoeba, we 
find no circulating nutritious fluid. When we 
ascend higher in the scale we find a colourless fluid 
containing molecules moving in certain definite 
directions by the action of cilia in the general 
cavity of the body, as in a sea-anemone. Still 
higher we meet with a colourless fluid circulating 
in vessels, frequently communicating with the 
body-cavity, and propelled by a special contractile 
organ, as in the sea-urchin or ascidian ; and at 
last we meet with a coloured fluid, circulating in 
vessels separate from the body-cavity, and having 
a propelling organ, or heart, of more or less 
complex structure, as in all the vertebrata. This 
fluid, in the higher animals and in man, is derived 
from three sources : ist, from materials absorbed 
in the primary digestion of the food in the ali- 
mentary canal ; 2d, from the secretions of certain 
glands called blood-glands, found in various parts 
of the body ; and, 3d, from materials re-intro- 
duced into the blood from the tissues, which are 
products of the decomposition and solution of 
portions of these tissues consequent on their vital 
activity. The so-called blood-glands are — the 
spleen, a large organ found almost in juxtaposition 
with the left end of the stomach ; the suprarenal 
capsules, two organs found in the lumbar region, 
one on the top of each kidney; the thymus, a 
gland found in the thorax, immediately behind the 
breast-bone, of larger size before birth and during 
the earlier years of life than during adult life ; the 
thyroid, a gland existing in front of the box of 
the larynx ; the pituitary and pineal glands, 
found in the brain \ the glands of Peyer, in the 
mucous membrane of the small intestine ; and 
lastly, the lymphatic glands, which we find in 
many parts of the body, such as in the groin, 
the armpit, the neck, &c. and which we 
readily recognise as hard 'kernels' during the 
inflammation of any adjoining part. All of these 
glands agree in certain points of their anatomy ; 
they have no ducts to carry off the secretion, 
except we regard the numerous lymphatics by 
which they are supplied as such ; they consist 
essentially of shut sacs, containing numerous 
molecules, nuclei from which cells may be de- 
veloped, and fully formed cells resembling \yhite 
blood corpuscles ; and finally, they are richly 
suppHed with blood-vessels, lymphatics, and 
nerves. That they are really connected with the 
formation of blood, more especially of the colour- 
less corpuscles, is probable from the fact, that in a 
disease known as leucocythaemia, in which there 
is a great increase in these cells, we find also that 
one or more or all of the blood-glands are much 
enlarged. 

9. THE BLOOD AND ITS CIRCULATION. 

The blood is the most important and most 
abundant fluid in the body, and deserves the 
popular term of the * vital fluid.' With the excep- 
tion of a few tissues, such as the centre of 
the cornea of the eye, the nails, and the hair, 
it pervades every part of the body, as may be 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



1 



shewn in the case of the skin by puncturing any 
part of it with a needle. The total quantity is 
estimated at about one-eighth of the weight of the 
body, or about 20 lbs. in a man of average size. Its 
colour is red, but it varies from a bright scarlet in 
the arteries to a dark purple in the veins. When, 
however, a minute drop is examined under the 
microscope, it is seen to be made up of, first, 
a clear colourless fluid; and, secondly, of a 
multitude of smaU solid bodies or corpuscles, 
which float in the plasma. This plasma, called 
liquor sanguinis, is composed of water richly 
charged with materials derived (through the 
chyme) from the food ; namely, albumen, fibrine, 
various fats, &c. The greater part of the blood — 
about 70 per cent. — is made up of water. It con- 
tains a very small amount of fibrine, about 7 per 
cent, of albumen, 14 per cent, of corpuscles, and 
the remainder consists of extractive matters, fats, 
and various salts. The great majority of the cor- 
puscles are of a yellowish-red colour, and by their 
enormous number seem to impart a red hue to the 
blood ; while a few are white or colourless. The red 
corpuscles have a diameter of about xsWth of an 
inch, being about ith of that fraction in thickness ; 
and in form they are circular biconcave discs, and 
in freshly drawn blood they arrange themselves 
by contact of their flat surfaces into little rolls 
like piles of coins. The colourless corpuscles 
are larger, globular in form, and present a 
granulated appearance. 
Recently it has been 
shewn that these are 
little masses of living 
protoplasm, capable of 
spontaneous movement, 
and that they are iden- 
tical with the corpuscles 
found in purulent matter 
or pus. In all classes 
of animals the colour- 
less corpuscles are alike ; 
but the form of the 
coloured corpuscles varies, being oval in fishes, 
reptiles, and birds. In all mammals they are 
circular, with the exception of the camels and 
llamas, where they are oval. Shortly after its 
removal from the body, the blood begins to thicken 
or coagulate, and soon separates into two distinct 
parts, one of them being a dark-red jelly or clot, 
which is the heavier of the two, and sinks ; while 
the other is a clear straw-coloured fluid, called the 
serum, which covers the clot. This depends on the 
formation of a substance called fibrine, which forms 
a meshwork of fine molecular fibres, entangling 
the corpuscles. When a coagulum appears, 
fibrine is produced by the union of two sub- 
stances present in solution, one called fibrino- 
gen, and the other termed fibrino-plastic sub- 
stance, the latter probably being a substance 
known as globulin, which forms a large part of 
the coloured corpuscles. This remarkable prop- 
erty of coagulation is the chief cause of the arrest 
of bleeding from a wound. 

The blood is in constant motion in a definite 
direction during life, and the motion is known as 
the circulation. Its true course was discovered 
by Harvey, about 1620. The organs of circulation 
are the heart, arteries, veins, and capillaries. The 
course of the blood through these organs will be 
best elucidated by the aid of a diagram, which 

118 




Fig. 2. — Blood Corpuscles 
highly magnified. 




a, aorta ; d, 
vena cava ; e, greater circula- 
tion ; b, smaller circulation ; 
f, pulmonary artery ; g, pul- 
monary veins. 



is equally applicable for all other mammals as well 
as for man and for birds. The shaded part of fig. 3 
represents structures filled with impure or venous 
blood, while the unshaded 
portion represents struc- 
tures in which pure oxy- 
genated arterial blood oc- 
curs. In this diagram 
we observe a dotted 
circle, representing a 
closed bag or sac, termed 
the pericardium, and in- 
closing the four cavities 
c, Vy c\ 1/ , of which the 
heart is composed. Two 
of these cavities, c and </, 
are for the purpose of re- 
ceiving the blood as it 
flows into the heart, and 
are termed the auricles ; 
while the two cavities, v 
and t/', are for the purpose 
of propelling the blood Fig. 3. — Mode of Circula- 
through the lungs and tion in Man and other 
general system respec- Mammals, and in Birds : 
lively, and are termed the *. heart ; v, right ventricle ; t/, 
ventricles. The vessels J^f reft'aullJie' ""^ ""'''' 
that transport blood into 
the auricles are termed 
veins; and the vessels 
through which blood is 
driven onwards from the ventricles are known as 
arteries. The diagram further shews that what we 
commonly term the heart is in reality two distinct 
hearts in apposition with each other ; one, shaded 
in the figure, which is called the right, or venous, or 
pulmonary heart ; and the other, unshaded, which 
is called the left, or arterial, or systemic heart, the 
last name having been given to it because the 
blood is sent from it to the general system ; just 
as the right heart is termed pulmonary from its 
sending blood to the lungs. We will now trace 
the course of the blood as indicated by the arrows 
in this diagram, commencing with the right 
auricle, c. The right auricle contracting upon the 
venous or impure blood which has been returned 
from the body, and with which we suppose it to be 
filled, drives its contents onwards into the right 
ventricle, v, through an opening between these 
two cavities, called the right auriculo-ventricular 
opening, which is guarded by a valve, named 
tricuspid, from its being composed of three 
pointed membranous expansions, which almost 
entirely prevents the regurgitation or reflux of the 
blood from the ventricle into the auricle. The 
ventricle, v, being now filled, contracts ; and, as 
the blood cannot return into the auricle, it is 
driven along the shaded vessel, the dividing 
branches of which are indicated by f. This 
vessel is known as the pulmonary artery, and 
conveys the blood to the lungs. At its commence- 
ment it is guarded by valves, termed, from their 
shape, the semilunar pulmonary valves, which 
entirely prevent the blood which has once been 
propelled into the pulmonary artery from re- 
entering the ventricle. The pulmonary artery 
gradually divides into smaller and smaller branches^ 
which ultimately merge into capillaries. In these 
capillaries, which are freely distributed over the 
external surface of all the air-cells (of which the 
lung is mainly composed), the venous blood is 



HUMAN PHYSIOLOGY. 



brought in contact with atmospheric air, gives off 
its carbonic acid gas (which is its principal 
impurity), and absorbs oxygen, by which pro- 
cesses it is converted into pure or arterial blood. 
The capillaries, b, in which the blood is arte- 
rialised, gradually unite to form minute veins, 
which, again, join to form larger vessels, until 
finally the blood is collected into four vessels, 
known as pulmonary veins (two from each lung), 
which pour their contents into the left auricle. 
Only one such vessel, g, is shewn in the figure, 
because the main object of this diagram is to 
illustrate the mode and general direction in which 
the blood circulates, not to indicate the special 
vessels through which it flows in different parts of 
the body. The blood, now fitted for the various 
purposes of nutrition, enters the left auricle, d, 
which, by its contraction, propels it into the left 
ventricle, z/, through the left auriculo-ventricular 
opening. This opening, like the corresponding 
one in the right heart, is guarded by a valve, 
which, from its form, is termed the mitral valve, 
and which entirely prevents the reflux of the blood. 
The left ventricle, i/ , contracts and drives its 
contents into the large artery, a, which repre- 
sents the aorta — the great trunk — which, by means 
of its various branches (none of which are indi- 
cated in the diagram), supplies every portion of 
the body with pure arterial blood. From the 
aorta and its various subdividing branches the 
blood passes into the capillaries, e, which occur in 
every part of the system. In these capillaries it 
undergoes important changes, which may be con- 
sidered as almost exactly the reverse of those 
which occur in the pulmonary capillaries ; it parts 
with its oxygen, becomes charged with carbonic 
acid, and, as it leaves the capillaries and enters 
the minute veins formed by their union, presents 
all the characters of venous blood. The veins 
gradually unite till they form two large trunks, 
termed the superior and inferior vence cavce, which 
pour their contents into the right auricle — the 
point from which we started. Only one of these 
great veins, d, is indicated in the diagram. We 
thus perceive that there is a complete double circu- 
lation ; that there is a lesser circulation effected 
by the blood in its passage from the right to the 
left heart through the lungs, and that there is 
a great circulation effected i)y that fluid in its 
passage from the left heart, through the system 
generally, to the right heart. 

The heart is situated in very nearly the centre 
of the cavivy of the chest. Its form is somewhat 
conical, the lower end tapering almost to a point, 
and directed rather forwards and to the left. This 
lower portion alone is movable, and, at each con- 
traction of the heart, it is tilted forwards, and 
strikes against the walls of the chest between, in 
man, the fifth and sixth ribs, or a little below the 
left nipple. All the large vessels connected with 
the heart arise from its base, and serve, from their 
attachment to the neighbouring parts, to keep that 
portion of it fixed. 

The substance of the heart is composed of a 
spiral arrangement of no less than seven layers of 
muscular fibre. When the ventricles contract, the 
blood is prop>elled from them, not in a direct 
manner, but with a sort of spiral motion, as if it 
were really wrung out of the heart. 

But although the heart is the chief organ for 
propelling the blood, there are other forces at 



work. When the right ventricle contracts, blood 
IS propelled into the aorta, which, however, con- 
tained blood at the time. This blood is pushed 
forwards, and the aorta dilates. When the pro- 
pulsive power has ceased, the aorta, being a very 
elastic tube, recovers its original calibre. In 
doing so, it assists in forcing the blood onwards. 
Thus by successive portions of the larger arteries 
acting in the same manner, dilating with the 
impulse, and regaining their size by elasticity, 
the original mechanical force of the heart, 
which throws blood into the aorta in a series 
of successive jets, is converted into a uniform 
wave-like flow, which we term the pulse. The 
Pitlse, which beats about seventy times per minute, 
is the change produced in the diameter and length 
of an artery when it receives the wave of blood. 
The tissues also exert an attractive influence on 
the blood, drawing it forwards ; and, consequently, 
we find that wherever we have activity of growth 
in any part of the body, there is a determination 
of blood to that part. We see this in the conges- 
tion which precedes the annual growth of a 
stag's horn. After the blood has passed through 
the capillaries and into the veins, the power of 
the heart has reached a minimum. The blood is 
now forced along the veins to the heart, chiefly 
by the pressure of the muscles. The veins are 
provided with valves, which are so arranged as to 
allow the blood to flow only towards the heart ; 
and, consequently, when a muscle contracts and 
presses on a vein, the blood is propelled forwards. 
Thus muscular exercise assists occasionally in 
removing venous congestions. Lastly, the move- 
ments of respiration affect the circulation ; inspira- 
tion, by increasing the flow of blood along the 
great vessels to the heart ; while expiration has the 
contrary effect 



lO. RESPIRATION. 

The organs and process of respiration now 
claim our attention. We have already stated 
that the blood of the arteries differs in colour 
from that of the veins, the former being of a 
bright scarlet tint, while the latter is purplish 
in colour. The arterial represents pure, and the 
venous impure blood ; the change from the former 
to the latter having taken place in the capillaries 
which form the bond of union between the ter- 
mination of an artery and the beginning of a 
vein. The chemical differences between arterial 
and venous blood are slight, except in relation 
to the gases held in solution in these fluids. The 
two kinds of blood differ widely in this respect, 
there being a smaller quantity of oxygen, and a 
greater quantity of carbonic acid in venous than 
in arterijil blood. 

The organs by which the impure and dark 
venous blood is converted into pure, bright scarlet 
arterial blood, fit for nourishing the various tissues 
of the body, are the lungs, and the agent by which 
this change is effected is the oxygen of the air we 
breathe. In their simplest form, as they occur 
in certain reptiles, they are mere air-sacs, existing 
as two elastic membranous bags, having small 
honey-comb-like depressions on their inner surface, 
communicating with the external air by a tube 
known as the windpipe, or trachea, which opens 
through the larynx or organ of voice into the throat 
These bags are lined by a delicate, thin, and moist 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



4 



mucous membrane, in which is imbedded a net- 
work of capillaries, through which all the blood 
is in turn driven by the heart. The moist par- 
tition between the blood in this network and 
the air in the interior of the lungs, is so thin as to 
allow an interchange between the gases of the 
blood and the gases of the air ; that is to say, 
oxygen passes from the air in the air-cells into 
the blood, while carbonic acid gas and aqueous 
vapour pass outwards from the lungs into the air 
in the air-cells. This is a purely physical phenom- 
enon, dependent on the laws of diffusion and 
admixture of gases through animal membranes. 




Fig. 4. 

In the higher animals and in man, these essential 
parts are much complicated and modified in a 
variety of ways. The anatomical details may be 
considered under the following heads. Firstly, the 
lungs must afford by their internal arrangement 
an immense extent of internal mucous membrane, 
covered by vascular network, through which, as 
in the simpler form, the blood flows in innumerable 
minute streamlets, only separated by an extremely 
thin membrane from the atmospheric air that 
has been inhaled ; secondly, there must be such an 
arrangement of the circulating system, that fresh 
blood may be perpetually driven from the right 
side of the heart through the lungs, and onward 
to the left side of the heart ; and thirdly, there 
must be arrangements for the frequent and regular 
change of the air contained in the lungs. 

We shall first consider the lungs and the pass- 
ages leading to them. The back of the mouth 
or pharynx is connected with the outer air in two 
ways — namely, by the nasal passages and nostrils, 
and by the mouth. Through either of these 
channels, the air may pass to and from the 
lungs, but the nostrils are, properly speaking, 
the entrances to the respiratory system. Behind 
the root of the tongue, we find a chink or 
aperture, the glottis, bounded laterally by two 
folds of membrane called the vocal chords, 
which may be more or less widely separated from 
each other. This chink or aperture is guarded 
by a leaf-like lid, the epiglottis, which can be 
closed when expedient, so as to prevent the 
120 



entrance of particles of food, drink, &c. The 
glottis opens downwards, into a box-like chamber 
called the larynx (which is the organ of voice), 
and leading downwards from the larynx runs the 
trachea, or windpipe, which is kept permanently 
open for the passage of air, by cartilaginous rings, 
that surround the anterior two-thirds of it. These 
are united, and the back of the tube is formed by 
a fibrous membrane or muscle. The windpipe, 
which is easily felt by the hand, and lies just 
below the projecting part of the larynx, popularly 
known as Adam's Apple, is about four and a 
half inches in length, and about three-fourths of 
an inch wide. Passing into the cavity of the 
chest, it divides into two branches, which are 
termed the right and left bronchi. Each bronchus 
enters the lung of its own side, and divides 
into a great number of smaller tubes, called 
the bronchial tubes, which again go on subdivid- 
ing. These finest tubes end in elongated dilata- 
tions, averaging T^th of an inch in diameter, 
which are called the air-cells. If we can con- 
ceive a bunch of grapes with its stem and all 
its minute branches, and the grapes attached 
to the ends of them to be hollow, we get a good 
idea of the mode in which the lung is con- 
structed, except that it does not represent all the 
sacculation or partitioning of the terminal cells. 
It is in consequence of the air included in these 
cells that the lungs have their soft spongy feeling, 
and crackle when compressed between the fingers. 
Each lung is invested by its own investing serous 
membrane, termed the pleura, which serves the 
double purpose of facilitating the movements 
necessary in the act of respiration, and in sus- 
pending each lung in its proper position. 

The blood is being perpetually changed and 
driven in a constant current through the lungs 
by the action of the heart, the venous or impure 
blood being collected in the right ventricle, and 
thence conveyed by the pulmonary artery into 
the lungs. In these, again, it gives off carbonic 
acid and aqueous vapour, and absorbs oxygen (as 
already described) ; and after these changes, it is 
collected, and returned to the left auricle by four 
vessels called the pulmonary veins. 

The mode in which the air is renewed in the 
lungs next requires notice. This is effected by 
the respiratory movements, which consist in alter- 
nate acts of inspiration and expiration, with an 
intervening pause before the process is renewed. 
An adult man in a sitting position performs the 
respiratory act from thirteen to fifteen times in 
the minute, but much more rapidly if taking 
exercise. At each inspiration, about 30 cubic 
inches of air are inspired, and at each expiration 
nearly the same volume is exhaled, difference 
being allowed for temperature, which in the ex- 
haled air may equal that of the blood. From 
300 to 400 cubic feet of air thus pass through 
the lungs of a man at rest in the course of 
twenty-four hours, and these are charged with 
carbonic acid, and deprived of oxygen to the 
extent of nearly 5 per cent. ; or, to put it in 
another form, about 18 cubic feet of the one 
gas are taken in, and of the other gas are given 
off. The quantity of carbon thus excreted in the 
form of carbonic acid gas is nearly represented 
by eight ounces of pure charcoaL The amount 
of watery vapour separated by the lungs varies 
from six to twenty ounces daily, according to thi 



' 1 
1 



HUMAN PHYSIOLOGY. 



diet, exercise, temperature, humidity of the air, 
&c. 

The mechanical means by which these changes 
are effected are partly to be sought for in the 
elasticity of the lungs themselves, and partly in 
the mobility of the sides and bottom of the cavity 
of the chest, which is thus enabled to alter its size 
with each respiratory act. The sides of the chest 
are mainly formed by the ribs, which are so 
attached to the spine as to be freely movable 
upwards and downwards by two sets of inter- 
costal muscles. Again, the diaphragm, the great 
muscular partition between the chest and the 
belly, is always convex to the former ; but when 
it contracts, the convexity is lessened, and con- 
sequently the capacity of the chest is increased. 

A knowledge of the respiratory process explains 
the .great benefit to be derived from efficient 
ventilation. Ten thousand parts of ordinary 
atmospheric air contain from 2 to 4 parts of 
carbonic acid. If this gas be present to the 
extent; of i^ to 3 parts in 1000, headache and 
giddiness are felt; and if it be increased to 20 
parts in looo, death will in all likelihood be the 
result. To secure a proper degree of dilution of 
carbonic acid in a small room, so as to render the 
air fit for respiration, about 2000 cubic feet of 
fresh air should be introduced every hour. 

II. THE NOURISHMENT OF THE TISSUES. 

The various tissues of the body, such as muscle, 
bone, nerve, or brain, are nourished by the blood. 
But as this fluid is almost the same in chemical 
composition in different parts of the body, and as 
the tissues differ much in this respect from each 
other, we must adopt the theory that each tissue 
has an elective power in itself, whereby it selects 
from the blood exactly the material it requires for 
its growth. To secure healthy nutrition, we must 
have an adequate supply of blood. If any part 
of the body is not supplied with abundance of 
blood, its actions are enfeebled ; and if the supply 
be cut off altogether, it soon weakens and dies. 
The blood must also be healthy in quality. If 
affected by disease of any organ, so that certain 
injurious materials are not eliminated, the general 
nutrition of the body speedily suffers. To secure 
proper nutrition, a part must, thirdly, be subject 
to the influence of the nervous system. Disease 
of the spinal cord causes paralysis of the lower 
limbs, and the muscles become soft, flabby, and 
diminish in luze. Section of a nerve supplying a 
part is often followed by destruction of the part 
by ulceration. Finally, the part itself must be 
in a healthy condition to secure proper growth. 
Any tissue which has acquired any peculiarity of 
structure by previous disease, retains this pecu- 
liarity for many years ; but in course of time the 
tissue tends to revert to its original condition. 
This explains such phenomena as the perpetua- 
tion of cicatrices, and the influence of the vaccine 
virus. In the latter case, the virus stamps a 
peculiar quality on the blood and tissues, which 
modifies any subsequent attack of small-pox. 
Growth is dependent essentially on the supply 
of material to the tissues by the blood, and on 
the amount of waste of tissue. If the supply 
exceeds the waste, as in childhood, the body in- 
creases in weight and power ; if the supply and 
waste are equal, the body may remain in a station- 



ary condition for many years, as in middle life • 
and if the supply is much less than the waste the 
body loses weight and strength, as in old age. 

12. SECRETION. 

Secretion is that function by means of which 
certain fluids are separated from the blood for 
further service in the economy. Various of these 
secretions, such as the saliva, gastric juice, pan- 
creatic juice, &c. have been already described, 
but here we may briefly refer to the process of 
secretion generally. However complicated the 
structure of the various secreting glands may be, 
it is found, on minute examination, to consist of a 
delicate membrane, called a basement membrane, 
having blood-vessels richly distributed under its 
attached surface, and actively growing cells on 
its free surface. By foldings and reduplications 
of these elements of structure, all secreting glands 
are formed. The cells, however, are the active 
agents. They select from the blood the materials 
necessary, and form the secretion. Recent re- 
searches have shewn that these cells are directly 
influenced by the nervous system. The secre- 
tion is found in their interior. They are de- 
veloped, grow, live a certain time, drop off from 
the membrane, and, becoming ruptured, the 
secretion is set free. Thus secretion is not op- 
posed to growth, as at one time supposed : it is 
dependent on the growth of certain cells. 

13. EXCRETION. 

During the vital activity of the tissues, new par- 
ticles are assimilated by the process of growth 
already described. On the other hand, certain 
materials are worn out, and becoming soluble, 
pass into the blood. These effete matters must 
be removed from the blood, and cast out of the 
body, so that this important fluid may be kept in 
a healthy condition. This process of removal is 
the function of excretion- There are five gjreat 
channels of excretion : 

1. The Lungs. — The lungs, as already described 
under Respiration, separate from the blood car- 
bonic acid and watery vapour. 

2. The Liver. — This organ is the largest and 
heaviest gland in the body, weighing, on an aver- 
age, 65 oz. avoirdupois. It is situated on the right 
side, beneath the lower ribs. It consists of five 
lobes, of a dark reddish colour, and these lobes 
are divided into lobules. The lobules are bound 
together by areolar tissue, and their structure 
is similar. The liver is supplied with the 
blood from which it derives its secretions by 
the portal vein, a vessel which collects all the 
blood circulating in the stomach, spleen, and 
intestines. The portal vein divides and sub- 
divides in the liver, till it forms a plexus of minute 
vessels between and in the lobules, from which 
originate the radicles of the hepatic vein, a 
vessel which carries the blood from the liver to 
the ascending vena cava. The connective tissue 
of the liver, and its vessels and nerves, are sup- 
plied by a special artery, the hepatic artery. 
The proper secreting structure of the liver con- 
sists of numerous compressed cells, about the 
TsV^th of an inch in diameter, called hepatic 
cells. These cells secrete materials from the 
blood, which they elaborate into bile. This 
secretion passes into minute ducts, the hepatic 

131 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



ducts, the exact mode of origin of which is 
at present obscure. These ducts convey the 
bile out of the liver ; and after it has become 
inspissated and mixed with mucus, from small 
mucous glands in the larger ducts, and from the 
gall-bladder, it is poured into the duodenum. The 
liver performs at least three functions : first, the 
secretion of bile ; second, the formation of fat ; 
and third, the formation of animal starch or 
glycogen. The bile is to be regarded chiefly as 
an excretion rich in hydro-carbons, but during its 
passage from the economy, it performs certain 
functions referred to under Digestion. It is highly 
probable that part of the bile is re-absorbed into 
the blood, but its ultimate function is unknown. 
The amount formed daily is about 3^ pounds ; 
but the quantity is liable to great variation. 

The formation of animal starch by the liver is 
called its glycogenic function. It is supposed that 
this starch, formed in the cells of the liver, is con- 
verted by the blood of the hepatic vein into sugar, 
which is carried to the lungs, where it is decom- 
posed into carbonic acid and water. This, how- 
ever, is a point not yet conclusively settled. 

3. The Skin. — This organ, continuous at various 
points with the internal 
mucous surfaces, covers 
the whole body, and 
consists of two layers : 
first, a hard epithelium, 
composed of cells more 
or less flattened, called 
the epidermis ; and 
second, of the derma, or 
cutis vera, or true skin, 
which is formed of con- 
nective and elastic tis- 
sue. Underneath the 
true skin, we find a 
layer of fat We find 
in the skin two kinds 
of glands. The sudorip- 
arous or sweat glands, 
consist of a tube, coiled 
into a ball at the deeper 
part, and communi- 
cating with the surface 
by a spiral duct. The 
sebaceous glands are 

Fig. 5. —Vertical Section of small racemose glands, 

tiie Skin of the Sole : which usually open into 

a, cuticle; b, papillary struc- the hair follicles, and 

ture; c cutis vera or true secretC an oily fluid 
skin; a, sweat-gland lying va. r i v • .• ..i -l • 

a cavity on tht deep surface for lubricating the hairs 

of the skin, and imbedded in and Surface of the skin. 

globules of fat Its duct is -pUp rhipf PYrrptinn nf 

seen passing to the surface. \"^ V"^^' CXCretlOn Ot 

Magnified about 30 diameters. Skin IS SWeat, an aCld 

watery fluid, which is 
usually carried off from the surface in the form of 
vapour. The amount varies greatly : from five 
pounds in the twenty-four hours, to one pound. 
That the separation of this excretion is important, 
is proved by the fact, that if the skin be varnished 
over, so as to prevent exhalation, death may 
speedily ensue. All the various modifications 
of epidermis, such as hair, horn, nail, hoof, &c. 
may also be regarded in the light of excretions, 
but space compels us merely to allude to this 
fact 

4, The Kidneys. — The human kidneys are situ- 
ated in the loins, one on each side of the spine. A 




well-developed healthy kidney weighs about six 
ounces. When cut open, we find a cavity com- 
municating with the ureter, the excretory duct 
of the kidney, and we observe also that the organ 
consists of two substances, which are named, from 
their position, the external or cortical, and the 
internal or medullary substance. The medullary 
part consists of straight tubules, which divide in 
two as we pass outwards to the cortical part, while 
in the latter, the tubes are extremely convoluted. 
In the cortical part of an injected kidney, there 
are numerous small round balls of capillaries 
called Malpighian bodies, after the celebrated 
anatomist who first observed them. In man they 
are about the rUth of an inch in diameter. They 
consist of a mass of minute capillaries supplied 
with blood by an afferent vessel, and having also 




Fig. 6. — Plan of the Renal Circulation : 

a, terminal branch of the artery, giving the terminal twig, af, to 
the Malpighian tuft, tn-, from which emerges the efferent vessel, 
ef. Other efferent vessels, e, e, e, are seen proceeding from other 
tufts, and entering the capillaries surrounding the uriniferous 
tube, t. From this plexus of capillaries the emulgent vein, ev, 
springs. 

an efferent vessel to carry the blood away. Each 
of these little balls is embraced by the dilated end 
of one of the uriniferous tubes, as seen in the 
preceding figure. The function of the kidney is 
to excrete urine, a fluid rich in nitrogenous 
materials. The urine is an amber-coloured liquid, 
having a specific gravity of 1020, a slightly acid 
reaction, a saltish taste, and an odour peculiar to 
itself. The chief substance in the urine of man is 
urea, of which about an ounce is excreted daily, 
while, during the same time, about eight grains of 
uric acid are separated. In reptiles, however, the 
amount of urea is small, while uric acid is largely 
present. These substances are derived from the 
waste of the nitrogenous tissues, uric acid being 
formed before urea. In rapid-breathing, warm- 
blooded animals, uric acid is rapidly oxidised to 
urea, and consequently only a small amount of the 
acid appears in the urine ; whereas, in slow- 
breathing, cold-blooded animals, the oxidation is 
incomplete. Man being omnivorous, partakes of 
enough of food rich in carbon to prevent the com- 
plete oxidation, and therefore a small amount of 
uric acid is always found in his urine. The kid- 
neys also separate inorganic matters, such as 
chlorides, sulphates, phosphates, &c. These are 
much modified as to amount by the nature of the 
diet, and the amount of fluid taken with them. 

5. The Intestines. — The excretions from the 
bowel consist not only of the non-nutritious mate- 
rials of food, bile, mucus, and mineral matters. 



HUMAN PHYSIOLOGY. 



but also of fetid effete matters removed from the 
system by the lower boweL 



II. THE FUNCTION OF INNERVATION. 

The vital processes included under the function 
of nutrition belong to the class of functions known 
as vegetative, because certain of them are common 
to vegetables as well as to animals. These func- 
tions have as their object the preservation of the 
plant. The animal has, however, another set of 
organs, by the use of which it becomes conscious 
of a world external to itself. By means of certain 
functions, which, from their occurrence in animals 




Fig. 7. — Human Adult Brain : 
a, anterior lobe of cerebrum ; 6, middle lobe ; c, posterior lobe of 
cerebrum, appearing behind ; d, cerebellar hemisphere ; e, medulla 
oblongata ; /, fissure of Sylvius ; g, longitudinal fissure ; A, k, 
olfactory bulbs ; t, optic commissure — the optic nerves are seen 
interchanging fibres ; /, three roots of olfactory process ; m, white 
round bodies (corpora albicantia), the terminations of the anterior 
portions of fornix ; «, where the vessels perforate the brain sub- 
stance, hence called posterior perforated space ; o, third pair of 
nerves coming to supply muscles of the eyeball, from /, the crus 
cerebri ; q, fourth nerve, turning round from the valve of Vieus- 
sens ; r, fifth pair ; « , pons varolii ; t, sixth pair of nerves ; u, 
seventh pair, purtio dura for muscles of face, and portio mollis 
for hearing ; v, posterior pyramids of cerebellum, seen to inter- 
change fibres ; in, and two below, are eighth pair — viz. glosso-pha- 
ryngeal, vagus or pneumo-gastric, and spinal accessory nerve ; 
between lu and v is the small prominence called olivary body ; 
*t ft two roots of ninth pair of nerves, motor nerve of tongue. 

only, are termed animal, all the higher creatures, 
and especially man, are endowed with Sensation, 
Motion, and Volition. These powers are due to 
the presence of a Nervous System, including two 
sets of nerves and nerve - centres — namely, the 
cerebrospinal system and the sympathetic system. 

The former consists of the cerebrospinal axis, 
composed of the brain and spinal cord, and the 
cerebral and spinal nerves connected with this 
axis ; while the latter consists chiefly of a double 
chain of ganglia or nervous masses, lying at the 
sides of the spinal column, and united with one 
another and with the spinal nerves by connecting 



threads of nervous tissue. The sympathetic 
system influences the heart and blood-vessels, and 
the intestines. It has the power of stimulating 
the action of the heart by acting on ganglia in 
its substance. It maintains the blood-vessels in 
a certain state of contraction. 

The cerebro-spinal axis lies protected in the 
cavity of the skull and spinal column, and is 
covered by three membranes, which serve for 
protection and for the supply of blood. 

Nerve-matter is of two kinds, white and gray, 
and may be readily seen by cutting through the 
brain of a sheep or of any other animal, when it 
will be observed that there is an outer layer of 
gray matter, while the interior is white. In the 
spinal cord these relations are reversed, the gray 
matter lying in the centre. The nerves consist 
entirely of the white tissue. The microscope 
shews that the gray matter is made up of round, 
oval, or star-like cells with a nucleus, and sending 
off prolongations, which either unite with those of 
other similar cells, or are continued as nerve-tubes. 
These cells, termed nerve-cells, vary much in size, 
from the TrrWth to the rlirth of an inch. The 
white matter consists of tubes, transparent as glass 
when examined alive ; but immediately after 
death, shewing two well-defined lines on each side 
of a broad clear space. They thus appear to con- 
sist of two parts — a central part, which probably 
conducts the nervous influence, surrounded by a 
substance, of different chemical constitution, which 
may act as an insulator of the nervous force. A 
nerve consists of many of these tubes running 
alongside of each other, and here and there 
plexuses are formed by certain tubes diverging and 
running from one nerve to another. The function 
of the nerve-tube is to receive an impression of 
any kind, mechanical, chemical, thermal, or voli- 
tional, thereupon to generate an influence, and to 
conduct this influence to or from a nerve-centre. 
The rapidity of the nerve-current is from 75 to 120 
feet per second ; incomparably slower than light, or 
electricity. The nerve-cells either receive or orig- 
inate nervous force. 

The brain consists of the cerebrum, or brain 
proper, which occupies the whole of the upp>er and 
front parts of the cavity of the skull ; the cerebellum, 
or little brain, lying beneath the hinder part of the 
cerebrum ; and the medulla oblongata, or oblong 
marrow, which may be regarded as a continuation 
of the spinal cord within the cavity of the cranium, 
and as forming the connection between the brain 
and cord. The cerebrum and cerebellum are 
almost completely bisected into two lateral halves 
by a deep longitudinal fissure ; and the surface of 
the former is divided by a considerable number of 
tortuous furrows, nearly an inch deep, into convo- 
lutions. As the gray matter is extended into these 
furrows, its quantity is thus vastly increased. 

At the base of the cerebrum, and connected 
with it, there are two large ganglionic masses of 
gray and white matter, called the corpora striata; 
behind these, other two bodies of a similar nature, 
the optic thalami; and still farther back, four bodies, 
two on each side, the corpora quadrigemina. All 
these parts of the brain are connected with each 
other by numerous tubes. The tubes from the 
spinal cord pass upwards in the medulla oblongata ; 
those from the posterior part of the cord going 
chiefly to the cerebellum, while those from the 
anterior pass to the cerebrum. In the cerebnun, 

* 123 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



I 



cerebellum, and ganglia, we also find tubes running 
from their anterior to their posterior ends, while 
other tubes run transversely, and unite correspond- 
ing parts on opposite sides of the brain. Thus 
there is evidently community of function. 

The functions of these different parts may be 
briefly stated to be as follows : i, the cerebrum is the 
seat of Sensation, Volition, Emotion, and of those 
intellectual powers which constitute Mind ; 2, the 
cerebellum is probably the regulator of muscular 
movements ; 3, the corpora striata is a great centre 
of voluntary movement, not of volition, but of the 
nervous mechanism by which, when we will with 
the cerebrum, the influences are sent along the 
spinal cord to the various muscles ; 4, the optic 
ihalami perform the same function with regard to 
sensation ; 5, the corpora quadrigemina receive 
visual impressions by the optic nerves from the 
retina of the eyes, and transmit these to the cere- 
brum, where there is then the consciousness of 
sight ; and 6, the medulla oblongata, and an 
adjoining part called the pons Varolii, are the 
seat of the nervous influences which regulate 
swallowing, breathing, and other important invol- 
untary movements. The parts of the brain last 
mentioned (6) are absolutely essential to life. The 
other parts may be cut or mutilated without in- 
stant death, but this surely follows in a few 
moments injury to the medulla. 

Nerves have different functions. When an in- 
fluence travels along a nerve to a muscle, it excites 
the muscle to contract, and the former is then 
called a motor nerve ; when it travels to the brain 
and causes a sensation, we call such a nerve sen- 
sory. Most nerves contain both sensory and motor 
tubes. Some are purely sensory, as certain parts 
of the fifth cranial nerve ; others purely motor, as 
the facial, or seventh cranial nerve ; while all the 
spinal nerves are senso-motory. Certain nerves 
respond only to particular stimuli. For example, 
the optic nerve is affected only by vibrations of 
rays of light. Such are called special sensory 
nerves, and include those of sight, hearing, taste, 
smell. The nerves of touch are those of common 
sensibility distributed to the skin. 

Twelve pair of nerves are given off from the 
brain, and thirty-one from the spinal cord. 

The spinal cord or marrow is a cylindrical 
column of soft nervous tissue, extending from the 
base of the skull, where it is continuous with the 
medulla oblongata, to the region of the loins, 
where it tapers off to a thread in the lowest part 
of the vertebral canal. Its average length is 
eighteen inches. It is not only divided by two 
fissures in the middle, but each half is again 
divided longitudinally into three equal parts by 
t\vo parallel series of nervous filaments, which are 
the anterior and posterior roots of the spinal 
nerves. The posterior root presents a swelling or 
ganglion, immediately beyond which the two 
coalesce into the trunk of a nerve which, after 
emerging through a hole called the intervertebral 
foramen, is distributed into branches to the parts 
it is destined to supply with nervous filaments ; 
as, for example, the muscles of the trunk and 
limbs and the surface of the body. These roots 
have separate functions, the anterior being com- 
posed of motor, while the posterior contain 
sensory tubes. Hence if the anterior root (in 
a vivisection operation) is divided, or if the 
column of the cord from which it springs is dis- 
121 



eased, loss of motion in the part which it sup- 
plies is the result ; while if the posterior root were 
similarly acted on, there would be loss of sen- 
sation. The anterior columns of the medulla 
decussate (that is, send nerve-tubes across to the 
adjoining column) ; while many of the tubes of 
the posterior columns decussate all the way up 
the back of the cord. Consequently, injury to 
the right anterior column causes loss of motion 
on the same side, while injury to the right pos- 
terior column paralyses sensation as regards the 
opposite side of the body. The decussation of the 
anterior columns in the medulla also explains how 
a clot of blood in the right hemisphere of the 
brain, as in apoplexy, causes loss of motor-power 
on the left side of the body. 

THE SPECIAL SENSES. 

There' are five senses — namely, touch, taste, 
smell, sight, and hearing. 

Touch. — The sense of touch, including that of 
different degrees of heat, is possessed by the 
skin, by the walls of the mouth and nostrils, and 
by the tongue, but it is most highly developed 
on the tips of the fingers. The essential organs 
of this sense are the true skin, containing capil- 
laries, and the terminations of sensory nerves. On 
examining the surface of the true skin by a magni- 
fying-glass, we can see a regular arrangement of 
papillae, or cone-like projections about rrsth 
of an inch in length. In many of these papillae 
there are found small round or oval bodies 
made of hard fibrous tissue, and having a nerve- 
tube coiled round them, and sometimes pene- 
trating into their interior. These are called touch- 
bodies. They serve as resisting structures against 
which the nerve may be pressed, and thus the sense 
of touch may be intensified. When one of those 
nerves is pressed by the contact of any foreign 
body, an influence is produced which travels to 
the brain, where we become conscious of the im- 
pression. This consciousness, however, we refer not 
to the brain, but to the part affected ; a subjective 
power, which is probably the result of experience. 

Taste. — The organs of taste are in the mucous 
membrane of the tongue, especially at its back 
part. The nerves of taste are the lingual branch 
of the fifth cranial nerve and the glosso-pharyn- 
geal, the former supplying the anterior two-thirds, 
and the latter the posterior one-third of the tongue. 
The mucous membrane of the tongue presents 
papillae of various forms, called yf/z/br;«, or thread- 
like ; fungiform, or mushroom-like ; and circum- 
vallate. The circumvallate are about thirteen or 
fifteen papillae set in the form of a V with its 
point backwards, and each resembles a fungiform 
papilte surrounded by a wall. These last-named 
structures are regarded as the essential organs of 
taste. They derive their nerves chiefly from the 
glosso-pharyngeal nerve. The contact of a sapid 
body with the surface of the tongue is not sufficient 
to evoke the sense of taste. The substance must 
be dissolved, and to effect its solution nature pro- 
vides a special fluid — the saliva. In febrile dis- 
eases, in which the tongue is dry and coated, the 
sense of taste is either dormant or perverted. 
Taste is more acute in some persons than in 
others. It is sometimes blended in a remarkable 
way with smell, giving rise to the peculiar sensa- 
tion we call flavour. The sensations produced by 



HUMAN PHYSIOLOGY. 



the contact of mustard, pepper, &c. with the 
tongue are not those of taste, but rather exag- 
gerated forms of touch. 

Smell. — The organ of the sense of smell is the 
mucous membrane lining a part of the nasal 
cavities supplied with nerves from the olfactory 
bulbs or first pair of cranial nerves. Attached to 
the side-walls of each nasal cavity are two delicate 
scroll-like bones, called turbinated bones, which 
to a great extent divide each cavity into three 
spaces, lying one above the other. The two 
uppermost of these constitute the true olfactory 
chambers, while the lowest passage is merely used 
for respiratory purposes. The whole of this bony 
framework is covered by moist mucous membrane, 
having imbedded in it flat elongated plates at- 
tached to the ramifications of the olfactory neives. 
By the contact of certain substances with these, a 
sensation of smell is produced. According to 
Graham, 'all odorous substances are in general 
such as can be readily acted on by oxygen.' 
Animal effluvia keep near the soil, hence the 
bloodhound runs with the nose to the ground. 
The sense of smell is extremely delicate in most 
individuals. It is soon blunted, and consequently 
many who live among disagreeable odours do not 

Eerccive them. A distinction must be drawn 
etween a smell proper, like that of a violet, and 
the irritation produced by the fumes of ammonia. 
The close stufify sensation experienced on enter- 
ing an ill-ventilated crowded apartment, is due 
chiefly to interference with the free play of respir- 
ation. 

Sight or Vision. — The sensation of Hght results 
from the influence produced on the sensitive expan- 
sion of the filaments of the optic nerve by vibra- 
tions of a delicate and subtle substance known as 




0> r>»i >:a,^J _ >- :: i>i 




Fig. 8. — A longitudinal section of the Coats of the 
Eye : 

I, the sclerotic, thicker behind than in front ; 2, the cornea ; 
3, the choroid ; 6, the iris ; 7, the pupil ; 8, the retina : 10, the 
anterior chamber of the eye ; 11, the posterior chamber ; 12, the 
crystalline lens, inclosed in its capsule ; 13, the witreous 
humour, inclosed in the hyaloid membrane, and in cells formed 
in its interior by that membrane ; 15, the sheath ; and i6, the 
interior of the optic nerve, in the centre of which is a email 
artery. 

* ether.' But the falling of light upon the optic 
nerve itself will produce no sensation. An inter- 
mediary apparatus is necessary — the retina, which 
is an expansion of nervous matter placed behind 
the optic nerve. 

The globe of the eye is placed in the anterior 
part of the orbit, in which it is held in position by 



its connection with the optic nerve posteriorly 
and with the muscles which surround it, and by 
the eyelids in front; It is further supported 
behind and on the sides by a quantity of fat. 
The eyeball is composed of several investing 

j membranes, and of certain transparent structures, 
which are inclosed within them. These trans- 

! parent structures act as refractive media of 
different densities, stf that rays of light entering 
the eye are so bent as to come to a focus on the 
retina. Thus a distinct image is formed. These 

j refractive structures are from before backwards— 

I 1st, the cornea, like transparent horn ; 2d, the 
aqueous humour, like water ; 3d, the lens, like 
glass ; and lastly, the vitreous humour, like clear 
jelly. 

The outermost coat of the eye is the sclerotic 
(from skleros, hard). It is a strong, dense, white, 
fibrous structure. Posteriorly, it is perforated by 
the optic nerve. This coat, by its great strength 
and comparatively unyielding structure, maintains 
the inclosed parts in their proper form, and serves 
to protect them from external injuries. 

The choroid coat is a dark-coloured vascular 
membrane, containing pigment cells. In front, it 
ends by means of the ciliary processes, which 
consist of about sixty or 
seventy radiating folds. 
These fit into depressions 
in the suspensory ligament 
of the lens, and assist in 
keeping it in its proper 
position. 

The iris may be regarded 
as a process of the choroid, 
with which it is continu- 
ous. It is a thin flat cur- 
tain, hanging vertically in 
the aqueous humour in 
front of the lens, and per- 
forated by the pupil for 
the transmission of light. 
It is composed of un- 
striped muscular fibres, 
one set of which being 
arranged circularly round 
the pupil, and, when neces- 
sary, effecting its contrac- 
tion ; while another set lie 
in a radiating direction 
from within outwards, and 
by their action dilate the 
pupil. Thus more or less 
light may be admitted into 
the eye, and its function is 
like that of the diaphragm 
in many optical instru- 
ments. 

The varieties of colour , ^ . 

in the eyes of ^^^^^^v.^ ^^^l^^:^::l^X::tfX. 

mdlVlduals and of differ- external granular layer ; 3, 

ent kinds of animals, 
mainly depend upon the 
colour of the pigment, 
which is deposited in cells 
in the substance of the 
iris. 

Within the choroid is the retina. With the 
naked eye it is seen to be a delicate semi-trans- 
parent sheet of nervous matter, lying imniedi- 
ately behind the vitreous humour, and extendmg 



fe: 



Fig. 9. — A Vertical Sec- 
tion of the Human 
Retina : 



the intervening layer be- 
tween 2 and 4, the inter- 
nal granular layer; s, finer 
granular layer; 6, layer of 
nerve-cells ; 7, fibres of the 
opiic nerve; 8, limitary mem- 
brane. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



II 



from the entrance of the optic nerve nearly as 
far as the lens. On examining the retina at the 
back of the eye by an instrument called an 
ophthalmoscope, we observe, directly in a line 
with the axis of the globe, a circular yellow spot 
called, after its discoverer, the yellow spot of 
Sommering. The only mammals in which it 
exists are man and the monkey. It is the point 
of distinct vision. When we read a book, we 
run the eye along the lines so as to bring portions 
of the line successively on the yellow spot. If, on 
the other hand, we carefully fix our attention on a 
word in the middle of the line, we see the word 
distinctly, because it is on the yellow spot, while 
the words towards each end of the line are less 
distinct, being on other portions of the retina. 

The structure of the retina, as revealed by the 
microscope, is seen in fig. .9. 

The transparent media through which rays of 
light must pass before they form on the retina the 
images of external objects are : 

Immediately behind the transparent cornea is the 
aqueous hutnour, which fills up the chamber be- 
tween the cornea and the lens. It is nearly pure 
water, with a trace of chloride of sodium. 

The crystalline lens lies opposite to and behind 
the pupil, close to the iris, and its posterior surface 
is received into a depression on the forepart of 
the vitreous humour (see fig. 8). In form, it is a 
double-convex lens, with surfaces of unequal cur- 
vature, the posterior being the most convex, and 
the curvature is also less at the centre than 
towards the margin. 

The vitreous humour lies in the concavity of the 
retina, and occupies about four-fifths of the eye 
posteriorly. 

The appendages of the eye are : 

1. The muscles by which the eye is moved are four 
straight (or recti) muscles, and two oblique (the 
superior and inferior). By the duly associated 
action of these muscles, the eye is enabled to move 
(within definite limits) in every direction. 

2. The eyelids are two thin movable folds placed 
in front of the eye, to shield it from too strong 
light, and to protect its anterior surface. The 
eyelashes intercept the entrance of foreign par- 
ticles directed against the eye, and assist in 
shading that organ from an excess of light. 

3. The lachrymal apparatus consists of the lach- 
rjTnal gland, by which the tears are secreted ; 
two canals, into which the tears are received near 
the inner angle of the eye ; the sac, into which 
these canals open ; and the duct, through which 
the tears pass from the sac into the nose. The 
constant motion of the upper eyelid induces a 
continuous gentle current of tears over the surface, 
which carry away any foreign particle that may 
have been deposited on it. 

The various uses of the different structures of 
the eye are readily understood. Assuming a 
general knowledge of the ordinary laws of geo- 
metrical optics, we will trace the course of the 
rays of light proceeding from any luminous body 
through the different media on which they impinge. 
If a luminous object, as, for example, a lighted 
candle, be placed at about the ordinary distance 
of distinct vision (about ten inches) from the front 
of the eye, some rays fall on the sclerotic, and 
being reflected, take no part in vision ; the more 
central ones' fall upon the cornea, and of these 
some also are reflected, giving to the surface of 

126 



the eye its beautiful glistening appearance ; while 
others pass through it, are converged by it, and 
enter the aqueous humour, which probably, also, 
slightly converges them. Those which fall on 
and pass through the outer or circumferential part 
of the cornea are stopped by the iris, and are 
either reflected or absorbed by it ; while those 
which fall upon its more central part pass through 
the pupil. The rays now impinge upon the lens, 
which, by the convexity of its surface, and by its 
greater density towards the centre, very much 
increases the convergence of the rays passing 
through it. They then traverse the vitreous 
humour, whose principal use appears to be to 
afford support to the expanded retina, and are 
brought to a focus upon that tunic, forming there \ 
an exact, but inverted image of the object. 

Accommodation of the Eye to Distance.— It will 
be found on experiment that we cannot see a dis- 
tant and a near object at the same moment. For 
example, if we look through a railing at a distant 
church spire, and fix our attention on the spire, 
we do not distinctly see the railing ; and vice versd. 
This was early observed ; but, until recently, the 
mechanism by which the eye accommodates or 
focuses itself for diffei-ent distances was unknown. 
Cramer was the first to point out that if we bring 
a candle-flame near the eye in a dark room, we 
may see three images — ist, an erect image reflected 
on the cornea ; 2d, an erect image on the anterior 
surface of the lens ; and 3d, an inverted and very 
faint image on the posterior surface of the lens. 
He also shewed that when the eye looks quickly 
at a near object, after having been for some time 
directed to a distant one, the middle image moves 
forward nearer to the first, and also becomes 
smaller, shewing that for near vision the anterior 
surface of the lens becomes more convex. Helm- 
holtz afterwards, by means of an instrument called 
the ophthalmometer, measured the sizes of those 
reflections, and, from certain data, calculated by 
mathematical formulae the radii of curvature of 
the reflecting surfaces ; and he shewed conclusively 
that the accommodation of the eye for different 
distances is eff'ected by changes in the curvature 
of the anterior surface of the lens. The physio- 
logical explanation is as follows : 

The lens, which is elastic, is kept habitually in 
a state of tension by the pressure of the suspensory 
ligament, and consequently has a flatter form than 
it would take if left to itself. When the ciliary 
muscle contracts, it relaxes the ligament, and 
thereby diminishes its elastic tension upon the lens. 
The lens, consequently, becomes more convex, 
returning to its former shape when the ciliary 
muscle ceases to contract. 

There are two common forms of defective vision 
which require notice — namely, short-sightedness 
or myopia, and long-sightedness or presbyopia. 
They are due to an abnormality either in the 
curves or in the density of the refracting media. 
In short-sightedness from too great a refractive 
power from either cause, the rays from objects at 
the ordinary range of distinct vision are brought 
too soon to a focus, so as to cross one another, 
and to diverge before they fall on the retina ; the 
eye in this case being able to bring to the proper 
focus on the retina only those rays which were 
previously diverging at a large angle from a very 
near object. The correction for this deficiency 
is accomplished by interposing between the ey« 



HUMAN PHYSIOLOGY. 



and indistinctly seen objects a concave lens, with 
a curvature sufficient to throw the images of 
external objects at the ordinary distance of distinct 
vision backwards upon the retina. In long-sighted- 
ness, on the other hand, there is an abnormal 
diminution of the refractive power, so that the 
focus is behind the retina. This defect is corrected 
by a convex lens, which increases the convergence 
of the rays of light. 

Position of Objects on the Retina. — In conse- 
quence of the bending of rays of light by the re- 
fractive media, the image of an external object is 
inverted on the retina, and yet we see objects 
erect. The probable explanation is, that the mind 
may perceive as correctly from an inverted as 
from an erect image. When we glance at a 
column from top to base, we move the eyeball 
downwards so as to bring successive parts on the 
yellow spot, and it is the feeling of movement 
which informs us which is top and which is base, 
not the inverted position on the retina, of which 
we are really unconscious. 

Single Vision with two Eyes.—T\\\s pheno- 
menon is explained by the fact that there are 
corresponding points on the retina, so that when, 
by the regular action of the muscles of the eyeball, 
an image is formed on a corresponding point in 
each eye, the mind is conscious of one image. If 
we alter the direction of the axis of one eye by 
pressing gently on the ball, an image is formed on 
a point of the retina of that eye which does not 
correspond, and consequently we squint, or see 
two images. 

Hearing. — The organ of hearing is composed of 
three portions, the external, middle, and internal 
ear. The external ear consists of the auricle, which 




vibrations of the air. The tympanum communi- 
cates with the back of the throat by the Eusta- 
chian tube, the function of which is to equalise 
atmospheric pressure on both sides of the vibrat- 
ing membrane. When this tube becomes stopped 
mechanically by enlargement of the tonsils, partial 
deafness is the result, and when cleared so as 
again to allow air to pass into the tympanum, 
hearing at once returns to its normal state. Across 
the tympanum, we find a chain of small bones, 
one of which, the malleus, or hammer, is attached 
by a long handle to the drum ; this unites by a 
joint with another, the incus, or anvil ; which in 
turn bears the stapes, or stirrup, the base of this 
being fixe^ to a small oval membrane closing an 
aperture, called the fenestra ovalis, which commu- 
nicates with the internal ear. The function of this 



Fig. lo. — General view of the External, Middle, and In- 
ternal Ear, shewing the interior of the auditory canal, 
tympanic cavity, and Eustachian tube : 

a, the auditory canal ; b, the tympanum ; c, the Eustachian tube, 
leading to the pharynx ; d, the cochlea ; and e, the semicircular 
canals and vestibule, seen on their exterior by the removal of the 
surrounding bony tissue. 

presents elevations and depressions, the functions 
of which are to receive and reflect the vibrations 
of the air which constitute sound, and to transmit 
these by a tube, partly cartilaginous, partly bony, 
called the auditory canal, to the middle ear. The 
middle ear is named the tympanum or drum. It 
is a cavity in the petrous or hard portion of the 
temporal bone. It is shut off from the auditory 
canal by the membrane of the drum, a thin struc- 
ture capable of vibrating when acted on by the 




Fig. II. — Ossicles of the Left Ear, as seen firom the out- 
side and below : 

m, head of the malleus ; e, the slender process, or processus gracilis ; 
k, the manubrium or handle ; sc, the short crus, and Ic, the long 
cms of the incus ; a, the position of the lenticular process, through 
the medium of which it articulates with the head of the sUpes a 
*, the base of the stapes. Magnified three diameters. 

chain of bones is to convey vibrations from the 
membrane to the internal ear. The internal ear, 
or labyrinth, so called on account of its complexity 
of structure, is the essential part of the organ of 
hearing, because here we find the filaments of the 
auditory nerve which are ultimately to receive 
impulses originally produced by vibrations of the 
air, and which are conveyed by the intermediate 
structures already described. It is made of three 
parts — the vestibule, or central part ; the seniicir- 
cular canals, three in number, which communicate 
posteriorly by five openings with the vestibule ; and 
the cochlea, so called from its resemblance to a 
snail-shell. Each of these parts is excavated from 
the substance of the bone, and forms the bony or 
osseous labyrinth ; but within this we have a fibrous 
structure, exactly corresponding in shape, the 
membranous labyrinth. The osseous is separated 
from the membranous labyrinth by a fluid called 
the perilymph, and within the membranous por- 
tion there is another fluid, called the endolymph. 
The terminations of the auditory nerve are dis- 
tributed on the walls of the membranous portion, 
and by the presence of the two fluids just men- 
tioned, the most delicate vibrations of the air 
communicated directly to the drum and cham of 
bones, or indirectly through the bones of the head, 
are conveyed to the nerves. The structure of the 
cochlea is very remarkable. It consists of a centr^ 
pillar, round which a tube makes two and a halt 
coils. This tube is divided into two comparttaents 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



by a partition, partly bony, partly membranous. 
The upper portion communicates with the vesti- 
bule, and, from its fancied resemblance to a 
stair, has been called scala vestibuli. Suppose we 
ascended this stair to the apex of the cochlea, we 
would there find a small opening communicating 
with the lower compartment, which has been called 
the scala tympani. It received this name because 
at the bottom it communicates with the tympanum 
by a round opening, called the fenestra rotunda, 
closed by a thm membrane. The cochlear branch 
of the auditory ner\'e enters the base of the pillar 
just mentioned, and distributes branches to the 
membranous portion of the scala:. But this is not 
all. Between the two scalae or staircases, in a 
triangular space, there is a remarkable organ, 
called the Organ of Corti. This is a com- 
plicated anatomical structure, which space will 
not allow us fully to describe here, but essentially 
it consists of three or four thousand jointed rods, 
apparently capable of vibrating, and presenting, 
when viewed from above, an appearance some- 
what like the key-board of a piano. 

We know little regarding the functions of the 
different parts of the internal ear. That they have 
different functions, we infer from the structure 
being so dissimilar, and also from the facts of 
comparative anatomy. In the animal kingdom, 
the vestibule first appears ; to this are superadded 
the semicircular canals ; and lastly, the cochlea, 
which increases in complexity from the lower 
orders of the mammalia up to man, in whom it 
is one of the most complicated organs of the body. 
The vestibule probably enables us to experience 
a sensation of sound as such ; the semicircular 
canals may, as suggested by Wheatstone, assist in 
determining the direction of sounds ; while there 
are many arguments in favour of the view, that 
the cochlea, as we find it in man, with a highly 
elaborated organ of Corti, may be the mechanism 
by which we appreciate musical sounds, which 
act so powerfully in exciting the emotions. 

The range of hearing, like that of vision, varies 
in different persons. Some are insensible to 
sounds that others hear. Many cannot hear the 
chirp of a grasshopper or the squeak of a bat, 
two of the shrillest sounds in nature. The range 
of the ear is much greater than that of the eye 
in detecting movements which produce vibrations. 
Thus we hear the sound produced by a vibrating 
rod or string long after we have ceased to see the 
movements. The range of the human ear is 
probably nine or ten octaves. 

The Muscular Sense. — There is still another 
sense, called the muscular sense, or sense of 
weight. If we close our eyes, and hold a weight 
on the palm of the outstretched hand, we ex- 
perience a peculiar sensation. It is not referable 
to any of the five senses, except, perhaps, to touch. 
But it is not simple touch. We are conscious of 
an effort to sustain the weight, and of a firm con- 
1S8 



dition of the muscles of the arm. This sensation 
is the muscular sense. It is the sensation we 
experience when any groups of the voluntary 
muscles are called into action, and by it we 
become aware of the condition of these muscles. 
By means of this sense, we stand erect, we walk, 
balance ourselves on a narrow ledge, throw stones 
or weapons, play on many instruments, &c. ; and 
it adds largely to our feelings of pleasure. 



VOICE AND SPEECH. 

There is a great difference between voice and 
speech. Voice is produced by vibrations of two 
thin folds of membrane called the vocal cords, 
placed in the larynx, at the top of the trachea or 
windpipe : speech is the modification of voice 
into sounds connected with certain ideas produced 
by the action of the brain, which we wish to com- 
municate to our fellow-men. Many animals have 
voice ; none, except man, have articulate speech 
expressive of ideas. The organ of voice is the 
larynx (behind the Pomum Adami), the struc- 
ture of which is very complicated, and cannot 
be here described. It consists of various car- 
tilages and muscles, the object of which is to 
tighten or relax the margins of two folds of mem- 
brane, called the vocal cords. By the vibrations 
of these cords voice is produced, and by tightening 
or relaxing, separating or approximating them, 
we obtain various modifications of voice. When 
a high note is sounded, the cords are tense and 
close together; and, on the contrary, when we sing 
a deep bass note, they are relaxed and wide apart. 
The quality and compass of the voice differ in 
individuals. In men, the highest is the tenor ; the 
lowest, the bass ; the intermediate, the barytone. 
In women, the corresponding notes are the 
soprano, the contralto, and the mezzo-soprano. 
The difference between the deep bass of a man 
and the shrill soprano of a woman, is, that in the 
man the cords are longer and less tense than in 
the woman. 

Speech is voice so modified by the action of the 
throat, tongue, cheeks, and lips, as to mean or 
indicate objects, properties, ideas, &c. This is 
language. If we breathe quietly, without causing 
the vocal cords to vibrate, and modify by the 
action of the mouth, &;c. the volume of air ex- 
pelled, we produce whispering. 



III. FUNCTION OF REPRODUCTION. 

The third great function of animal life is repro- 
duction, by which the species is perpetuated. It 
is beyond the scope of this article to treat of this 
subject, and reference is accordingly made to 
special works on Anatomy and Physiology. 



ZOOLOGY. 



¥h 



ZOOLOGY (from Greek zoon, an animal, and 
logos, a discourse) treats of the form and 
structure of animals, and the characters by which 
they may be distinguished from each other. 

AH natural bodies may be divided into two great 

oups — mineral or inorganic, and living or organic. 

he organic are again subdivided into -vegetables 
and animals. Hence arises the division of all 
natural objects into three great kingdoms — namely, 
the Mineral, Vegetable, and Animal. 

Inorganic stibstances never live. Chemically, 
they may be simple or compound, such combina- 
tions usually forming binary or ternary compounds. 
Their physical condition may be soUd, fluid, or 
gaseous ; but they are homogeneous in texture, 
2iat is, any detached portion exactly resembles 
the remainder in composition and properties. 
They may be amorphous, without distinct forms ; 
or crystalline, that is, having distinct geometrical 
forms, bounded by plane surfaces, which have a 
definite relation to each other. They increase by 
the addition of like particles to their surface, which 
is termed accretion ox juxtaposition. Their atoms 
are at rest, unless set in motion by some physical 
force acting from without : they initiate no change 
or motion. 

An organic being either lives or has lived during 
- some part of its existence. Chemically, it con- 
sists of few elements, which unite to form ternary 
and quaternary compounds. It consists of solid 
and fluid parts, which exercise a reciprocal action 
on each other. It is bounded by curved lines, 
and has convex and concave surfaces. Each 
organised being, under the influence of life, 
assumes a characteristic, though not absolutely 
definite shape. It increases or grows by receiving 
into its interior matter which it elaborates and 
assimilates. The old particles are being con- 
stantly removed, and replaced by new ones, so 
that all its parts are in constant motion, and are 
ever changing. It arises from some pre-existing 
organism of the same kind, by means of a germ, 
which becomes separated, and enjoys an individual 
existence. 

We do not know ' life ' apart from matter ; some 
material substratum or * physical basis ' is required 
for its manifestation. This, according to Huxley, 
is furnished by what he calls protoplasm, which 
is a homogeneous, structureless substance, en- 
dowed with contractility, and having a chemical 
composition nearly allied to that of albumen : it is 
composed of carbon, hydrogen, oxygen, and nitro- 
gen. This term life indicates a very special prop- 
erty indeed ; and at present, looking at it from a 
purely material point of view, we are scarcely justi- 
fied in regarding life as more than that condition 
of an organised being in which the products of 
chemical and physical changes taking place within 
it are stamped with a specie form. By the term 
'moulding of specific form' is meant the building 
up of a complicated and heterogeneous organism, 
which repeats the characters which have been 
transmitted to it through a germ, by a parent, 
9 



every molecule of every part having thus a direct 
relation in form, in position, and in composition, 
to every other molecule of the body. 

It is impossible to draw a distinct line of de- 
marcation between vegetables and animals, as 
the lowest forms of both kingdoms seem to meet 
and merge into each other. It was on this account 
that Professor Ernst Haeckel of Jena constructed 
a fourth kingdom, called by him 'Protista,' into 
which he proposed to put all the organisms of 
doubtful affinity. But this, at present, seems 
scarcely justifiable. Of course, the conspicuous 
members of the vegetable kingdom can never be 
confounded with the higher animal forms. In 
the latter, the presence of a nervous system, the 
possession of a mouth and digestive cavity, as well 
as the power of voluntary locomotion, are sufficient 
to distinguish them from the former, in which all 
these are absent. In the simplest groups in each 
kingdom, however, these grand distinctions are 
lost. Chemically, plants consist chiefly of ternary 
compounds — that is to say, compounds consisting 
of three elementary ingredients, as starch and cellu- 
lose, which are different combinations of oxygen, 
hydrogen, and carbon. In an animal, quaternary, 
and still more complex compounds, as albumen, 
fibrine, and gelatine, make up the bulk of the 
body ; while ternary compounds, though, indeed, 
not wanting, play a subordinate part. The general 
plan of nutrition is strongly contrasted in the 
two kingdoms ; but in some low animal forms, 
as the Gregarinae, nutrition is effected by absorp- 
tion through the external surface, just as is the 
case in plants. Most plants are permanently fixed 
in the ground by roots, but some low forms of 
algae are locomotive ; and although most animals 
can move about from place to place, others are 
incapable of progression, as the branched and 
tree-like sponges. It may be said, in a general 
sense, that organs of relation are present in 
animals, and absent from plants. But some 
phenomena coimected with climbing plants, and 
with the process of fertilisation, are very difficult 
to explain without admitting some low form of a 
general harmonising and regulating function, com- 
parable to such an obscure manifestation of reflex 
nervous action as we have in Sponges and other 
animals in which a distinct nervous system is 
absent. 

Plants can secrete and store in their leaves 
and other parts a substance called ' chlorophyl,' 
by means of which, under the influence of light, 
they absorb carbonic acid from the atmosphere, 
decompose it, and, when the carbon is in a 
nascent state — that is, just liberated from com- 
bination — can combine it with the elements of 
water (hydrogen and oxygen), or with the ele- 
ments of water and ammonia, hkewise reduced 
to a nascent state by the same agency. The 
plant thus gains from the air and from the soil 
certain elementary substances, chiefly carbon, 
oxygen, hydrogen, and nitrogen. These, under 
the guidance of a vital property, and through the 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



medium of protoplasm contained in its cells, it 
combines into still more complex organic com- 
pounds, which contribute to the development or 
maintenance of the special specific form of the 
organism of which it is a part. Plants can assimi- 
late no elementary substance except oxygen, unless 
it is presented to them in the nascent condition. 

An animal stands in exactly the same relation 
to the binary compounds, carbonic acid, water, 
and ammonia, which, along with salts, form the 
food of plants. An animal cannot assimilate these 
substances directly ; they must first be elaborated 
to the condition of ternary and quaternary com- 
pounds, which can be done only by the cells of 
Elants. This is the broad and practical distinction 
elween the vegetable and the animal kingdom. 
Plants possess &e power of absorbing, modifying, 
and organising inorganic substances ; while animals 
are entirely dependent for their support upon the 
organic substances thus prepared. 

The pale growing parts of plants have precisely 
the same vital properties and relations as animal 
protoplasm. It is only in cells in which proto- 
plasm elaborates and incorporates with itself 
colouring-matter (endochrome), which seems to be 
a more powerful catalytic agent, capable of dis- 
engaging the component atoms of the more stable 
binary compounds, when loosened by the vibra- 
tions of light, that the special function of the 
vegetable cell is manifested. Further, in the in- 
terior of the cells of some plants, as Chara, the 
movements of the protoplasm are so special and 
characteristic as to prove its absolute identity with 
the protoplasm of the Rhizopods. 

A living being is a complicated machine, which 
does a great deal of various work. One of the 
higher animals, to take an example, is made up of 
a great many parts, each of which does its own 
special part of that work — thus, the stomach 
digests, and the eye sees. These several parts are 
called organs, and the thing which an organ does 
is called \\% function. If we remove these organs, 
performing each its function, one by one, the 
whole animal disappears. The animal body 
therefore consists of the sum of its organs. 

Living beings may be studied under three 
principal aspects — the Morphological {morphe, 
form, and logos, a discourse), the Physiological, 
and the Distributional. 

Morpholo^. which treats of they57r»« and struc- 
ture of livmg beings, includes anatomy, both 
naked-eyed and microscopic ; to the latter, the 
term Histology {hisios, a web, and logos) has been 
applied. It also embraces Embryology, or the 
study of the forms of living beings in all stages of 
development, from their earliest or immature con- 
dition, tiU they reach their mature or adult state. 

Physiology XxtdXs oi the functions of the organism 
as a whole, or of its separate component parts, 
organs, or tissues ; of what an animal does, or of 
what its different parts do. The functions of an 
otganism are divisible into — i. Function of Nutri- 
tion. 2. Function of Generation or Reproduction. 
3. Function of Irritabilitry or Correlation. 

The function of nutrition has reference to the 
support and maintenance of the body. Matter is 
introduced into the interior of the body ; there it 
undergoes certain changes, which assimilate it to, 
and fit it to be incorporated with, the textures 
which compose the body. The function of repro- 
duction ser\'es the purpose of perpetuating the 

180 



species. The function of nutrition and the function 
of reproduction have been called the functions of 
' organic ' or ' vegetative ' life, because they are 
possessed both by plants and animals. The func- 
tions of relation — including irritability, conscious- 
ness, sensation, and volition, with all the move- 
ments depending upon the will — bring the organ- 
ism into connection with the outer world, and the 
outer world into connection with the organism, 
so that thus the one reacts upon the other. This 
group of functions is possessed by animals alone, 
so that they have been called the 'functions of 
animal life.' 

Distributioft treats not only of the areas of the 
globe ovel- which organisms are distributed, and 
the conditions under which they exist, but it also 
relates to the history of life in bygone ages, as 
furnished to us by the evidence of fossil remains. 
The former is called distribution in space, or 
geographical distribution ; the latter, distribution 
in time. 

Classification. — On looking at the multitude and 
variety of animal forms around us — such as we 
are familiar with as inhabitants of this country, or 
as natives of other climates collected for our obser- 
vation — the mind naturally associates together 
those which have the greatest general resem- 
blance, and separates these (although differing in 
some degree amongst themselves) from those 
with which they have greater dissimilarity. Now, 
it is necessary that some system of arrange- 
ment or classification should be adopted, by 
bringing together those animals which most 
closely resemble each other, not so much in 
external appearance as in internal structure, in 
order that the mind shall be the better able to 
grasp the facts of zoological science. A classifi- 
cation, therefore, will be correct in proportion to 
the number of ascertained facts upon which it 
is founded. Zoologists, in seeking to classify 
animals, are in the habit of using several terms, 
one of the most important being species. It is by 
no means easy to define this term. It is generally 
understood to mean an assemblage of animals 
that resemble each other in all essential points of 
structure, and which are supposed all to have 
descended from the same parent stock. A test to 
which much importance has been assigned, is 
founded on the supposed fact, that when the 
animals of different species breed together, their 
offspring is barren. This offspring is called a 
hybrid — thus, a mule is a hybrid between a horse 
and an ass. This, however, is not an absolutely 
satisfactory or conclusive test of specific identity, 
as hybrids between undoubtedly distinct species 
have been known, though rarely, to breed and 
produce fertile offspring. 

Until lately it has been the almost universal 
belief among naturalists that species are perma- 
nent within very narrow limits of variation ; that 
is to say, that any group of animals which present 
the same specific characters, characters which 
lead an educated observer to set them down as 
the same thing — for example, all common 
partridges, or, to take a variable species, all 
domestic dogs — are descended from an ancestry 
which can by no possibility include anything 
except partridges or dogs, and can never, under 
any circumstances, or through the lapse of any 
amount of time, give origin to anything except 
dogs or partridges. This view, of course, involves 



ZOOLOGY. 



the admission of the special creation of a single 
progenitor for each species, or of two, according 
as the sexes may be united or distinct. As 
Edward Forbes expresses it (Natural History of 
the British Seas, page 8): 'Every true species 
presents in its individuals certain features, specific 
characters, which distinguish it from every other 
species ; as if the Creator had set an exclusive 
mark or seal upon each type.' From time to 
time, however, naturalists of high eminence, and 
among them the celebrated French zoologist 
Lamarck, dissented from this view, and contended 
that the weight of evidence was rather in favour 
of a gradual development of the whole animal 
series from the simpler to the more complex ; a 
development comparable in certain respects to the 
development of the individual from the germ to 
maturity. 

The * doctrine of evolution ' has assumed various 
forms more or less plausible. It will be sufficient 
here to give a slight sketch of the latest of those 
speculations, the one which has received the 
widest acceptance, and exerted the most powerful 
influence upon the current of human thought — the 
* Darwinian theory' of the origin of species by 
natural selection. 

This speculation — for it cannot be said to have 
assumed anymore definite form — is based upon 
the known phenomena of variation. 

It is very evident that offspring have a ten- 
dency to resemble their parents very closely in 
form and structure ; and this resemblance, in all 
cases within our experience, brings parent and 
offspring within the limit of the same species. 

It is equally evident that offspring have a 
tendency to differ individually from their parents 
to a certain degree, but this variation is slight, 
involving no specific distinction ; and in no case, 
so far as we are at present aware, interfering with 
the power of reproduction, or with the fertility of 
the succeeding generation. 

The range of variation of the individuals com- 
posing a species is thus very definite, and is 
limited by the circumstances under which the 
group of individuals is placed. Except in man 
and in domesticated animals, in which it is 
artificially increased, this individual variation is 
usually so slight as to be inappreciable, except to 
a practised eye ; and any extreme variation which 
passes the natural limit in any direction clashes 
in some way with surrounding circumstances, and 
is dangerous to the life of the individual. The 
normal line or * line of safety ' for any species lies 
midway between the extremes of variation. 

If at any period in the history of a species the 
conditions of life of a group of individuals of the 
species be gradually altered ; if, for example, the 
temperature of the region which they inhabit be 
changed, or if there be an alteration in the amount 
or kind of food, with the gradual change of cir- 
cumstances, the limit of variation is contracted in 
one direction and relaxed in another ; it becomes 
more dangerous to diverge towards one side, and 
more desirable to diverge towards the other, and 
the position of the lines limiting variation is thus 
altered. The 'normal line' along which the 
specific characters are most strongly marked is 
consequently slightly deflected, some characters 
being more strongly expressed at the expense of 
others. This deflection, carried on for ages in 
the same direction, must eventually carry the i 



divergence of the varying race far beyond any 
limit within which we are in the habit of admit- 
ting identity of species. Those individuals in 
which the favourable variation is most marked 
will have the advantage in this struggle for life ; 
will be the stronger and the more comely, and 
will naturally select one another as partners for 
the perpetuation of the race; thus continuing 
and exaggerating the favourable peculiarity from 
generation to generation. 

We must admit that variation is a vera causa, 
capable, within a limited period, under favourable 
circumstances, of converting one species into 
what, according to our present ideas, we should 
be forced to recognise as a different species. 
And such being the case, it is, perhaps, conceiv- 
able that during the lapse of a period of time- 
still infinitely shorter than eternity — variation 
may have produced the entire result. There is 
no doubt great difficulty in imagining that, com- 
mencing from the simplest living being, the pres- 
ent state of things in the organic world has 
been produced solely by the combined action of 
' atavism ' and ' variation ; ' and many are still 
inclined to believe that some other law than the 
' survival of the fittest ' must regulate the existing 
marvellous system of extreme and yet harmonious 
modifications. Still, we are probably justified in 
saying that there is now scarcely a single com- 
petent general naturalist who is not prepared to 
accept some form of the doctrine of evolution. 
But the process must be infinitely slow. It is 
difficult to form any idea of ten, fifty, or a 
hundred millions of years, or of the relation which 
such periods bear to changes taking place in the 
inorganic world. But if it be possible to imagine 
that this marvellous manifestation of Eternal Power 
and Wisdom involved in living nature can have 
been worked out through the law of ' descent with 
modification ' alone, we shall certainly require the 
longest row of figures which the inexorable phy- 
sicists can afford. 

The origin of species by descent with modifica- 
tion is as yet only an hypothesis. During the 
whole period of recorded human observation, not 
one single instance of the change of one species 
into another has been detected ; and, singfular to 
say, in successive geological formations, although 
new species are constantly appearing, and there 
is abundant evidence of progressive change, no 
single case has yet been observed of one species 
passing through a series of inappreciable modi- 
fications into another. 

To a number of species agreeing in most points 
of importance, and having kindred characters, 
and these characters appealing broadly to the 
senses, the term genus — meaning a kind — is 
applied. From the arrangement of species of 
animals in genera has sprung the modem system 
of zoologicS nomenclature, first adopted by the 
celebrated Linnaeus. This system has received 
the name of the binomial system, from the fact 
that each animal receives two names, one belong- 
ing to itself alone, and the other which it possesses 
in common with the other species of the genus 
under which it is placed. Thus, the genus Equus 
contains the Ass, Horse, and Zebra as species. 
To all, the generic name Equus is applied ; but a 
second or specific name is added to each, to dis- 
tinguish it from all other species of the genus : 
thus, the Horse is called Equus caballus ; the 

' 131 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Zebra, Equus zebra; and the Ass, Equus asinus. 
A number of genera with more common characters 
are usually grouped as an order: for example, the 
Ruminant animals, as cattle, deer, &c form an 
order. Sometimes, however, a group of genera, 
with certain characters in common, is called a 
faniilys for example, the crow, jay, magpie, chough, 
&c. form the family Corvida. In these instances, 
a group of families forms an order. To a com- 
bination of orders, the term class is applied — for 
example, birds, fish, reptiles. Then we come to 
characters still more general, according to which 
the entire animal kingdom has been subdivided 
into six sub-kingdo»u. These have also been 
called morphological types, and are, as it were, 
the great ground-plans upon which the Divine 
Architect has constructed all animals. Thus, we 
have Sub-kingdoms, Classes, Orders, Families, 
Genera, Species, and Varieties, each term in 
succession being applicable in a more and more 
particular way than its predecessor. 

The six sub-kingdoms or morphological types 
of the animal kingdom are : 

I. Protozoa — for example, amoeba, sponges, infusoria. 
II. CtELENTERATA — for example, sea-anemones, sea- 
firs, corals. 

III. EcHiNODERMATA — for example, sea-urchins, star- 

fish. 

IV. Annulosa, or Ringed Animals — ^for example, in- 

sects, spiders, worms. 
V. MoLLUSCA, or Pulpy Animals — ^for example, sea- 
mats, oysters, cuttle-fish. 
VI. Vertebrata, or Back-boned Animals — for ex- 
ample, fishes, birds, reptiles, and man. 



stance and the outer layer ; there is neither mouth, 
contractile vesicle, nor nucleus. So far as we as yet 
know, the Monera in no case multiply by sexual 
reproduction. A portion separates as a bud, or an 



L SUB-KINGDOM PROTOZOA. 

The Protozoa (Gr. protos, first, zoon, animal — 
the beginnings of life) are usually minute, and 
many of them can be seen only by the aid of 
the microscope ; but sometimes they are of con- 
siderable size, for example, the sponges. They are 
formed of a jelly-like substance called 'sarcode,' 
or 'protoplasm,' which exhibits little or no trace 
of structure, resembling closely raw white of egg, 
more or less firm. In most is found a small 
soUd body, the ' nucleus,' which, from recent 
observations, appears to be an ovary ; and near 
this, one or tAvo still more minute particles, the 
* nucleoli,' which seem to be cells containing fer- 
tilising filaments. In many, contractile vesicles 
have been observed, spaces filled with a clear 
fluid which is driven by a contraction of the wall 
of the cavity through invisible channels in the 
body substance. Most are nourished by absorp- 
tion through the general surface. They do not 
possess a nervous system or organs of sense, 
neither is there any distinct digestive system. In 
nearly all, a mouth is absent, but it is present in 
one group. They are nearly all aquatic. 



CLASS 1. — THE MONERA. 

The Monera are the simplest of living beings. 
They consist of structureless, homogeneous, semi- 
fluid protoplasm, sometimes so soft and transparent 
that one can detect it only by its not mixing with 
the outer water. In this group there is no marked 
difference in consistence between the inner sub- 

132 




Protomyxa aurantiaca (after Haeckel). 

individual or a separated part contracts into a 
round ball, and becomes covered by a transparent 
layer ; the central mass then breaks up into, a 
multitude of grains. Finally, the outer covering 
bursts, and each of the grains becomes a separate 
'moner' of the same species. Notwithstanding 
their extreme simplicity, the Monera present 
specific and even generic distinctions. They differ 
in colour : Protomyxa aurantiaca^ described by 
Professor Ernst Haeckel, is bright orange. They 
differ likewise in habit Myxodictyum sociale of 
the same author lives in a colony, each of the little 
round moners being attached to a number of 
others by spreading sarcode threads. 

A large part of the bed of the North Atlantic at 
great depths is covered with a calcareous sediment 
composed almost entirely of the broken shells of 
Foraminifera, the group of Protozoa to be next 
mentioned. This lime-mud is usually slightly 
tenacious, as if a little size were mixed with it. On 
putting it under the microscope, this glairy matter 
separates into irregular strings, which shew move- 
ment This would seem to be a form of the 
Monera, even more simple than those which 
have a definite shape. To this ' Urschleim ' of the 
Atlantic chalk mud, Professor Huxley has given 
the name of bathybius. 



CLASS IL — RHIZOPODA. 

Gromia is the type. The sarcode body is 
inclosed in an egg-shaped membranous shell or 
* test,' which has a single opening at one end, 
whence issue long prolongations of its body. 
These are termed pseudo-podia (false feet). They 
have no limiting wall, but seem just to flow 
along in the water, and when two come in con- 
tact, they flow together. It has no mouth, but 
obtains its food by throwing out its pseudo-podia, 
which, when they encounter any substance, such 
as a minute diatom, gradually close round it, and 
then pull it into the interior of the shell, where it 
is digested by the sarcode ; and then the indi- 
gestible portions are expelled through the opening 
in the shell. 



ZOOLOGY. 



The Amoeba^ or Proteus animalcule, so called 
from the facility with 
which it can change its 
shape, possesses a nu- 
cleus and contractile ves- 
icle, and its pseudo-podia 
are blunt and club-shaped, 
but they do not flow to- 
gether. 

The Foraminifera have 
a calcareous * test,' perfor- 
ated by numerous small 
apertures, through which 
pseudo-podia are emitted, 
or a test made up of sand 
grains cemented together, 
and leaving openings for 
the ' false feet.' Some are 
simple, as Lagena, but 
most are composite, pro- 
duced by continuous gem- 
mation or budding, each 
to the body by which it 
bud remaining attached 
was put forth. Some 
shells have only a single aperture placed at one 
end," through which the pseudo-podia are pro- 
truded. According to the plan of this budding, 
so will be the form of the composite body pro- 
duced. In some, the parts are arranged in a 






Foraminifera : 
T. Lagena striata ; 2. Textilaria ; 3. Operculina. 

Straight row ; in others, a single row is rolled into 
a spiral; and in some the parts are in the same 
plane, or they may form a spire, with a more 
or less conical form, the first chamber being 
at the apex. All the chambers com- 
municate together by openings between 
adjacent chambers. They are marine, 
and exist in enormous quantities in the 
bed of the Atlantic, forming the chief 
part of the ' ooze,' which is composed 
almost entirely of a species of Glob- 
igerina {G. bulloides). 

The PolycistincE have a silicious 

instead of a calcareous shell, which is 

Podocyrtis. often most beautifully sculptured. They 

are all minute, and are frequently found 

in infinite multitudes, forming a coloured cloud 

on the surface of the sea. 



CLASS in. — GREGARINIDvE 

are parasitic in the intestines of some insects, 
and in the earth-worm. They are probably more 
allied to some low forms of Entozoa than to the 
Protozoa. 




CLASS IV.— PORIFERA OR SPONGIDEA. 

In the sponges, the Protozoa attain their largest 
dimensions, and their greatest prominence in the 
economy of the present time. The body consists 
of sarcode, which is supported by an internal 
skeleton or framework composed of carbonate of 
lime, of silica, or of horn, or of a combination of 
one of the former two with the latter. In the 
bath sponge, which is the best known example, 
the skeleton consists of a network of flexible homy 
fibres alone. When the sponge is taken living 
from the sea, it is completely filled and covered 
with the jelly-like living matter. A thin gelat- 
inous membrane, perforated with very small holes, 
covers the surface, and every here and there rises 
into a papilla with a large hole at the top. These 
larger openings are called oscula, and they open 
into a set of channels which divide and branch 
till they penetrate through the entire substance of 
the sponge. The pores in the outer wall likewise 
communicate with the ultimate meshwork of the 
sponge, and are thus in communication with the 
channels and the oscvda. The channels are lined 
with cilia — delicate hairs, which, by a perpetual 
lashing movement, drive the water along the 
channels ; or they have somewhere in their course 
chambers lined with cilia. The nutrition and res- 
piration of the sponge are thus conducted : water, 
with organic food in 
solution or suspension, 
and containing air, 
enters the pores, 
passes through the 
tissue of the sponge, 
and is exhausted by 
the absorbing sarcode 
surface. The effete 
water is then col- 
lected into the chan- 
nels, and urged for- 
ward by the cilia till 
it pours out at the 
oscula in a stream. 
True sexual reproduc- 
tion has not yet been 
established for spon- 
ges : they multiply by 
the separation of small, 
oval, ciliated buds, 
called gemtnuleSy 
which escape along 
with the water from 
the oscula. 

The principal orders 
of the Porifera are the 
Calcispongiae, the 
Hexactinellidae, the 
Ceratospongias, the 
Corticatte, and the 
Halichondrize. 

In the Calcispongice 
{calx, lime, and spog- 
gos, a sponge), the 
sarcode is supported 
by granular horny 
matter, mixed with 
three - rayed needles Hyalonema. 

or spicules of carbon- 
ate of lime. These sponges are found frequently 

133 




CHAMBERS'S INFORMATION FOR THE PEOPLE. 



round the coast of Britain, hanging from the 
under-side of rocks between tide-marks. They 
are all marine. The second group, the Hexac- 
tinellidcty so called from their spicules, which are 
always silicious, having usually six rays, seem to 
be confined to the deep sea, and are very abun- 
dant there. In this family we have some of the 
most singular and the most beautiful of natural 
objects. Venus' flower-basket {Euplectella asper- 
eilluni), from the seas of the Philippine Islands, 
is like a graceful horn-of-plenty wrought in an 
infinitely delicate tissue of spun-glass. Hyalonema, 
the Glass-rope Sponge of Japan, produces, grow- 
ing downwards from the centre of a small conical 
sfKjnge, a great wisp of glassy spicules, as thick 
as knitting-needles, and a couple of feet long, 
which penetrate the mud, and hold the sponge in 
its place, like a root. The upper part of this 
' glass-rope ' is almoSt always covered with a crust 
formed of a spreading zoophyte. This is a case 
of ' commensalism ' (Lat. con, together ; mensa, a 
table), an economical arrangement which is not 
at all uncommon in nature. Two animals live 
together habitually, one taking advantage of the 
excess of food procured by the other by means of 
currents produced by its cilia or some other 
like means, and doubtless contributing in some 
way to the comfort or 
support of its 'chum.' The 
bath sponge is the type 
of the Ceratospongice (Gr. 
keras, horn), distinguished 
by their soft flexible skele- 
ton of horn. The sponge 
of commerce is brought 
up by divers from water of 
moderate depth, the finest 
coming from the coasts 
of Syria and the Greek 
Archipelago, the greater 
number from the Bahamas. 
The CorticatcB (Lat. cor- 
Extemal surface and sec- tex, bark) include the glo- 
tional view of Living bular sponges, frequent in 
Sponge. deep water, with a thick 

outer bark bristling with 
long spicules, which spring in sheaves radiating 
from the centre. The Halichondrice (Gr, hah, the 
sea, and chondre, gristle) are the common sponges 
of the coasts of Britain, very abundantly incrusting 
stones and sea-weeds below tide-mark, and some- 
times shooting up into independent branching tufts 
or tubes. They are quite frush, and unfit for any 
use. Their skeleton is composed of a combination 
of homy granules or fibres, with silicious spicules 
of diverse and often very elegant forms. Nearly 
all the Porifera are marine. One genus, Spongilla, 
or fresh-water sponge, is common in the fresh 
waters of Britain. 



CLASS v.— INFUSORIA. 

The Infusoria are chiefly microscopic, and are 
found in all stagnant waters, or in any infusion 
which has been exposed to the air for some time — 
hence the name. They do not emit pseudo-podia. 
They possess a mouth, which leads into a sort of 
gullet, excavated in the soft gelatinous substance of 
the body ; but this gullet is not continued into a 
defined stomach or alimentary canal, the organic 

134 





Vorticellidas. 



matter introduced by the mouth passing into, and 
mixing with the sarcodic substance of the animal 
The mouth is generally surrounded by cilia (vibra- 
tile hair-like appendages), by which currents are 
formed in the water, and food brought into it 
In the body are a number of contractile vesicles, 
which pulsate at 
regular intervals, 
and may repre- 
sent a rudimen- 
tary heart Bur- 
saria swims freely 
about by means of 
the cilia placed all 
over its surface. 
The Bell Animal- 
cule, or Vorticella, 
is attached, and 
remains fixed like 
a plant.* The body 
is bell-shaped, the 
opening of the bell 
being surrounded 

with a ring of cilia, which, by their vibratile move- 
ments, bring food within reach. It is situated on 
a long stalk, which is capable of spiral contraction. 
This takes place on the slightest movement or 
alarm. 

Bacteria, Spontaneous Generation. — If a little 
weak wine, or a thin syrup of sugar, or an infusion 
of tea or of meat, be left exposed to the air, it 
very soon begins to ferment or to putrefy. In 
doing so, it becomes muddy ; and if a drop of the 
muddy liquid be placed under a microscope, it 
is found to contain myi-iads of excessively small 
living and moving beings, most of which must be 
referred to the Protozoa, though some are the 
germs of different kinds of mould (fungi). Two 
kinds are almost universal in sucb solutions — 
minute, transparent, oval bodies, slightly enlarged 
at each end, called bacteria; and very sniall rods, 
generally of two joints, called vibriones. No 
structure can be made out in either of these, but 
they are recognisable and distinguishable from 
other things, and they have a peculiar vibratile 
motion. A question has arisen, whether these 
creatures, which appear everywhere, are all pro- 
duced from germs of already existing creatures of 
the same kind, or whether they may originate in 
the liquid by the uniting of the substances required 
to form them, which are all contained in the liquid, 
the product then becoming alive. This latter 
process has been called * spontaneous ' or ' equivo- 
cal' generation. Does life ever originate in such 
a way? The following considerations seem to 
render it improbable. 

If a ray of sunlight pass through a chink, and 
traverse a dark room, its path is made evident 
as a long gray line of motes dancing in the vibrat- 
ing air. These motes settle down as dust ; and 
if a little of this be magnified, it is found to be 
mainly broken particles of wool and grains of 
starch ; but it contains germs as well ; for if a little 
dust be shaken into an infusion, we have a crop 
both of animals and plants at once. Here, then, 
is a source of germs which is imiversaL M. 
Pasteur, a French chemist, has shewn that if a 
flask be filled with a solution in which, if it were 
left open, bacteria would abound immediately ; 
and if it be entirely freed by heat from living 
germs and air containing such, and the neck of 



ZOOLOGY. 



the flask be then closed with a plug of cotton-wool, 
the liquid may remain for months quite clear. 

It is very difficult so to treat a vegetable or 
animal infusion, and to prevent even one of these 
infinitely minute and universally distributed par- 
ticles getting into it during the process. The 
consequence is, that in many flasks, notvvithstand- 
ing all precautions, bacteria do appear. One 
negative in such an investigation is, however, 
worth a thousand positive observations, and it 
would seem that the number of negative results is 
in proportion to the pains taken, and to the skill 
of the experimenter. All present evidence goes 
to shew that under no circumstances with which 
we are acquainted, does any living being arise, 
except as the progeny of a pre-existing living being 
of the same kind. 



II. SUB-KINGDOM CCELENTERATA. 

The Ccelenternta (Gr. koilos, hollow, enteron, an 
intestine) have their parts arranged round a central 
axis in a radiate manner, like the segments of an 
orange, and they are capable of being split into 
right and left similar halves. They are thus said 
to have radial and bilateral symtnetry. Further, 
each segment of the body can be divided into 
two symmetrical halves. They all have a distinct 
digestive cavity, which always communicates with 
the outer world by a mouth. In some, the diges- 
tive cavity is identical with the body cavity, the 
stomach being merely hollowed out in the gelatin- 
ous body substance ; and in others it is distinct, 
the wall of the stomach hanging as a free sac 
within the body cavity ; but in this latter case 
there are always free channels of communication 
between the digestive sac and the general cavity 
of the body. In the great majority, no circulatory 
or nervous system is developed. 
The body-wall is composed of two layers {ecto- 
derm, outer skin, and endo-derm, 
inner skin), which contain a number 
of peculiar bodies termed * thread- 
cells.' These thread-cells consist of 
an oval bag filled with fluid, within 
which is coiled a long and extremely 
slender filament provided with three 
recurved darts or barbs. On the 
application of the slightest force to 
the tensely filled bag, this filament, 
often several times longer than the 
_ bag, is projected outwards, and trans- 
thread - cells fixes and paralyses the prey, while 
of the Hydra, ^jjg flyj^ seems at the same time to 

with jts three . , , . . „ 

recurved barbs, exercise a benumbing influence upon 
it. Distinct reproductive organs 
are present in alL The Coelenterata are divided 
into two classes. 



CLASS I.— HYDROZOA. 

The digestive cavity is not separated from the 
body cavity, but is identical with it, and the repro- 
ductive organs are on the external surface of the 
body. Hydra is the type. It is usually seen 
attached to some aquatic plant or twig in our 
ponds and ditches. It is cylindrical in form 
and gelatinous in consistence, and usually about 
half an inch in length. It has at one end an 




One of the larger 




Hydra fusca : 



expanded disc, by which it attaches itself to any 
object; at the other is the 
mouth, which is surrounded 
by a tircle of arms or ten- 
tacles, which move about in 
all directions in the water. 
The body is composed of 
the two layers, armed with 
thread-cells, which are spe- 
cially abundant in the ecto- 
derm and in the tentacles. 
Small larvae and worms 
are its favourite food. To 
entrap these, it spreads out 
its tentacles, moving them 
gently in the water, to in- 
crease their chances. The 
prey is paralysed by means 
of the thread-cells, and is 
pushed through the mouth 
into the internal cavity, 
where it undergoes diges- 

tion, the indigestible por- with a young bud at*, and 
tions being Iinally expelled more advanced bud at f. 

through the mouth. It is 

not permanently fixed, but can detach itself, and 

move about in the water. 

Trembley of Geneva shewed that Hydra is 
exceedingly tenacious of life, and endowed with 
extraordinary reparative powers. It may be turned 
inside out and still live, or be cut into pieces, each 
of which may become a perfect hydra. It increases 
towards the end of the year by ova ; and during 
the summer months, by buds or getnmce, which 
sprout from the sides of the parent. At first, 
the stomachs of the bud and parent are con- 
tinuous ; but they become separated by a constric- 
tion, tentacles are formed at the free end, and it 
then separates as a perfect hydra. 

Order i. — Hydridce includes only the genus 
Hydra. Imagine a hydra going on budding, and 
the buds remaining attached to the parent — a 
tree-like arrangement would thus be produced. 

Orders 2 and 3. — This is almost constantly the 
case in the second and third orders, Corynida 
and Sertularidce (Sea-firs), and the animal is thus 
composite. It is usually permanently fixed, and 
is inclosed in a firm but flexible tube, which ex- 
tends only up to the base of the buds or polypites 
in the CorynidcBj but in the Sertularidce forms a 
little cup for each polypite, into which it can 
retract itself when alarmed. They are often found 
on the sea-shore, attached to old shells. The 
reproductive process in the Corynida and Sertu- 
laridce is certainly very peculiar. At certain 
seasons, some of the buds become modified in 
form and structure, so that they assume an 
appearance not unlike a Medusa. To these buds 
the term zooid is applied. After a time, these 
zooids or Medusa-like buds become detached 
from the parent stem, and swim about for some 
period, when there are developed in them the 
organs of reproduction. So closely do these 
zooids resemble the true Medusidce, that they 
were for a long time confounded with them. The 
ova and spermatozoa of these zooids now imite, 
and give rise to bodies having the appearance of 
a flattened disc covered with cilia, by means of 
which they swim freely about. This disc-like 
body becomes attached, part of it forming the root 
by which it is attached, while from its centre there 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



grows a single polypite, which by budding grows 
into a form exactly resembling the branched tree- 
like zoophyte, which gave origin to the Medusa- 
like bud. This is an example of what Steenstrup 
called ' alternation of generations,' although it is 




a, Hydromedusarium of Bougaittvillia superciliaris ; 
by Young Bougainvillia, or Medusoid bud, liberated 
firom the Hydromedusarium. 

not so in reality, there being only one truly gener- 
ative act — namely, when the ova and spermatozoa 
of the Medusa-like bud or zooid unite to produce 
the disc-shaped ciliated body. 

Order 4. — The Siphonophora, represented by 
Physalia (Portuguese man-of-war), Vellella, and 
by a midtitude of wonderfully beautiful oceanic- 
surface forms, such as Agaltna and Diphyes, which 
frequently swarm in the warmer seas, many of 
them forming branching feathery organisms several 
yards in length, and consisting of an infinite num- 
ber of glassy swimming-belts, feeding polypites, 
reproductive polypites, and filaments covered with 
thread-cells, many of their parts relieved and 
brightened by coloured spots, crimson, blue, or 
purple. Some have a float or inflated bag, which 
enables them to float on the surface of the ocean. 
Depending from the under-surface of the animal 
are a number of thread-like appendages, and a 
soft flexible stem, to the sides of which are attached 
numerous buds or polypites. These also repro- 
duce themselves by Medusa-like buds, like the 
Sertularia. 

Order 5. — The true MedusidcE have a 
swimming-bell, like an umbrella, composed of a 
jelly-like materiaL A single polypite is suspended 
from the centre of the concavity of the bell ; 
and, running inwards from its margin is a veil, 
perforated in the centre by an aperture, through 
which water is admitted into the interior of the 
bell, and is again expelled by its rhythmical con- 
tractions, so that the animal moves in a direction 
opposite to that in which the water is expelled. 
Four canals, radiating from the centre, run in its 
walls, and are joined at the circumference by a 
circular canaL Suspended from the margin of the 
bell is a number of tentacles, and on it are 
several coloured spots, which are supposed to 
represent rudimentary eyes. These Medusae pro- 
duce animals exactly resembling themselves. 

Order 6. — Discophora. In the interior of 

136 



old shells may be found an animal closely resem- 
bling Hydra, but sexless. It is called Hydra 
tuba. At certain seasons, a number of transverse 
markings may be seen upon a cone-like append- 
age growing from the free end of the hydra, which 
gradually deepen into annular constrictions, so 
that it looks like a pile of saucers. Each segment 
is thus a transverse segment of the cone-like body 
projecting from the free end of the hydra tuba. 
Each develops tentacles, and becoming detached, 
grows into a hooded-eyed Medusa. This, when 
perfectly developed, consists of an umbrella or 
swimming-bell, with one or more polypites sus- 
pended from its concavity. It has eight radiating 
canals, whose branches anastomose with each 
other ; but it has no veil. It has a number of 
tentacles suspended from the margin of the 
umbrella, and upon it are coloured eye-spots, and 
small cavities containing a fluid with crystals of 
carbonate of lime. These last are supposed to 
represent organs of hearing. Both of these are 
covered over by a fold of membrane like a 
hood, and hence 
the name 'hooded- 
eyed ' Medusae. 
They are often of 
enormous size, and 
are commonly 1 
called jelly-fish or 
sea-blubbers. They 
are represented by 
such forms asRhiz- 
ostoma and Pela- 
gia. These pro- 
duce ova, which 
again, in turn, give 
rise to hydra tuba, 
aflFording another 
example of the so- 
called 'alternation 
of generations.' The phenomenon of phosphor- 
escence of the sea is largely due to the Medusidae, 
and some of the Discophora, which, when irritated, 
emit sparks of light, or glow like globes of fire. 

CLASS II. — ACTINOZOA, 

The digestive sac is distinct from, and sus- 
pended in, the body cavity, communicating freely 
with it by an opening below. The space inter- 
vening between the stomach and the body-wall is 
called the ' peri-visceral space,' and is divided into 
a series of chambers by vertical partitions, to the 
faces of which the reproductive organs are at- 
tached. 

Actinia is the type {aktis, a ray). The body 
is short, and of fleshy consistence, attached at 
one end to a rock, and having at the other 
the mouth, surrounded by several rows of 
tentacles, which, from their arrangement and 
colour, like that of a full-blown many-petalled 
flower, have obtained for this animal its com- 
mon name of sea-anemone. The mouth leads 
into a stomach, opening at its lower end 
into the peri-viscerai cavity, which is divided 
by vertical partitions, having the reproductive 
organs attached to them. They feed upon shell- 
fish and other marine animals, which they draw 
into the mouth by the tentacles, disgorging shortly 
afterwards the shells and other indigestible parts. 
They are very sensitive to light, and expand or 




Rhizostoma. 



ZOOLOGY. 



close their tentacles according to the fineness of 
the day. When the feelers are drawn in, the 
apertures from which they proceed close like the 




Actinia seen from above. Section of Actinia : 

a, cavity of stomach ; b, sur- 
rounding chambers. 

mouth of a purse, and the animal appears like a 
simple fleshy tubercle adhering to the rocks. 

Order i. Zoantharia. — The Zoantharia have 
th« tentacles numerous and simple, while the 
radiating partitions are in multiples of five or six. 
They are represented by Actinia or Sea-anemone, 
many species of which occur along our shores. 
Some forms, however, are supported by a structure 
called a coral, which is composed of calcareous 
matter, or of homy matter, or partly of both. In 
one group this coral consists of a solid rod or 
axis, quite smooth on the surface, and presenting 
no appearance of cups, and merely acting as a 
support, over which the soft tissues of the animals 
are stretched. To a coral quite smooth and 
devoid of cups, the term sclero-basic is applied 
(Gr. scleras, hard, and basis, pedestal). The 
Black Coral {Antipathes), which is so much 
prized, has a sclero-basic coral, composed of 
homy and calcareous matter, forming a smooth, 
solid, branching structure, over which the tissues 
of the animal are stretched. In another group, 
the tissues of the animal are more or less com- 
pletely calcified, by the deposition of particles of 
carbonate of lime in their structure. Such a coral 
is called a sclera-dermic coral {scleras, hard, and 
derma, skin), and it can at once be distinguished 
from die former by the presence of the calcified 
cups for the polyps. Like the animal which pro- 
duces it, a sclero- 
dermic coral may 
be simple or 
compound. Thus 
Carophyllia is a 
simple coral, and 
consists of a cal- 
cified cup or cor- 
allite. The calci- 
fied boundary wall 
of this conical 
simple corallite is 
called the theca, 
the lower part of 
which is divided 
by a series of 
radiating calcified 
vertical partitions 
{feptd) into chambers or loculi, while the upper 
part is vacant. Many of these septa run from 
the interior of the theca, and meet in the centre, 
forming a columella or axial support. 

In a compound coral the various cups are united 
by calcareous matter, the whole exactly resembling 




Caryophyllia borealis. 



in form the animal which secreted it As examples 
of compound sclero-dermic corals may be cited 
the Brain QoxdXs {Meandrinci), and Star Corals 
{Asteriadce). Amongst simple sclero - dermic 
corals, the following are found off the coast of 
Britain in deep water — Lophohelia proli/era, 
Amphihelia ramea, Allopera oculina, and Caryo- 
phyllia borealis. 

Extensive reefs and many islands in the Pacific 
Ocean, Indian Sea, and throughout Polynesia, are 
composed of coral, the product of these minute 
polypes. Darwin has classified coral reefs into {a) 
atolls, {b) barrier reefs, and {c) fringing reefs. 

Fringing reefs skirt continents or surround 
islands. The channel between them and the land 
is shallow, and outside the. reef there is no great 
depth of water. 

Barrier reefs may encircle islands or skirt con- 
tinents. The channel between the land and the 
reef is navigable, and outside, the soundings in- 
dicate enormous depths. The reef on the north- 
east of Australia is 1250 miles long, and from 10 
to 90 in breadth, and rises from its seaward edge 
in some places free 1800 feet. 

Atolls are circular coral reefs inclosing an ex- 
panse of water, which is called a ' lagoon.' The 
circle has breaks in it here and there, and is 
generally highest towards the windward side, 
against which the waves are continually dashing 
with great violence. The coral-producing polypes 
cannot exist in fresh water, hence the breaks in the 
circle where a stream had poured its waters into 
the ocean ; neither can they exist at a depth of 
over 80 fathoms, or withstand the heat of the 
sun's rays. A mean winter temperature of not less 
than 66° is necessary for their existence. When 
a reef, by the gradual elevation of the land upon 
which it is placed, has reached the surface of the 
water, sand, shells, fragments of coral broken off 
by the waves, and other substances begin to 
accumulate, and cocoa-nut trees often grow while 
the waves still wash their roots. Further accumu- 
lations from the ocean, with decayed leaves, stems, 
&c. gradually convert the reef into fertile land. 
Mr Darwin shewed that a fringing might be con- 
verted into a barrier reef by the gradual sinking 
of the land on which the reef is built, the coral 
polypes gradually building upward; and by a 
further subsidence, a barrier reef might be con- 
verted into an atoll. This accounts for the great 
depth of some of the coral reefs that exist in the 
Pacific Ocean. 

Order 2. Alcyanaria — characterised by having 
the tentacles fringed, and the parts in multiples of 
four — includes Alcyonium, or * dead-man's fingers,' 




so called from its flabby appearance when seen in 
the fisherman's net It is a composite animal, and 
is studded all over with little pits, from which 
polypes protrude. Its body contains a few spicules, 
and is traversed by a system of canals, which 

isr 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



connect the various polypes together. Pennatula, 
the Sea-pen, has one end of the axis, which is sup 
ported by a sclero-basic coral, fixed in the sand in 
the sea-bottom. From this axis, lateral branches 
are given off, upon which are placed the polypes. 
Its colour is readish yellow, and when irritated, it 
shews phosphorescence. In Gorgonia (Sea-shrub), 
the coral is branched, homy, and sclero-basic. 
The Red Coral of commerce {Corallium rubntm), 
whose sclero-basic coral is so much admired for 
its fine colour and for ornamental purposes, has a 
smooth and branched tree-like form, about one 
foot in height, and is about the thickness of the 
little finger. It is chiefly obtained from the Medi- 
terranean, and is largely exported to India. 

Order 3. Ctenophora — are free - swimming 
ocean forms, which never develop a coral. They 
are gelatinous-like bodies, spherical in form, very 
delicate, and transparent Eight bands covered 
with cilia run from pole to pole. By the motion of 
these cilia, the animal moves along. A trace of a 
nervous system has been discovered in some forms, 
Bcroe piieus, which is like a globe of jelly, about 
half an inch in diameter, forms part of the food of 
the whale, and is often seen in the English Channel 



TIT. SUB-KINGDOM ECHINODERMATA. 

The Echinodermata {echinos, urchin, and derma, 
skin), or Spiny-skinned Animals, are so called 
because they have a crustaceous or coriaceous 
covering generally armed with tubercles or spines. 
They have their parts arranged radially, but they 
also exhibit bilateral symmetry. The alimentary 
canal is completely shut off from the body cavity. 
The integument covering the animal is more or 
less completely calcified by the deposition of cal- 
careous particles. In these animals there exists a 
peculiar system of tubes, called the ambulacral 
system {ambulo, I walk), because they are used 
for the purpose of progression. The nervous 
system consists of a gangliated nervous cord 
surrounding the conmiencement of the gullet, and 
sending branches which radiate outwards parallel 
with the ambulacral tubes. A blood-vascular or 
circulatory system is also present In their mode of 
reproduction, the members of this group exhibit 
some very peculiar phenomena. The embryo is 
at first free, swimming, and ciliated, and is pro- 
vided with distinct digestive organs, which do not 
become converted into the corresponding struc- 
tures of the adult This embryonic form has 
been called a pseud-embryo (false-embryo), bear- 
ing no resemblance to its parent; so much so, 
that the embryo of Echinus was at one time 
described as a distinct animal under the name of 
Pluteus. Only a part of this embryo is converted 
into the adult Echinoderm, the remainder entirely 
disappearing. The adult form is, as it were, 
a sprout from a particular part of this pseud- 
embryo. This sprout goes on developing a 
distinct mouth, digestive and other organs, until 
it exactly resembles the adult form which gave 
rise to the Pluteus. 

It contains several orders, two of which, the 
Blastoidea and Cystoidea, are entirely extinct 
Representatives of these two orders, such as 
Pentremites of the coal, and EchinosphcBrites of 
the Siliuian rocks, flourished during the Pdaeozoic 
age. 

138 



Order i. The Crinotdea, or sea-lilies, are fixed 
during the whole or part of their existence to the 
sea-bottom by a jointed and flexible stalk. They 
consist of a series of plates articulated together, 
forming a central cup or disc. From the edge of 
this cup there spring five arms, which bifurcate, 
and thus form ten beautifully fringed arms. Run- 
ning along the inside of the arms is a furrow, 
covered in by the skin of the disc, and from which 
are protruded the ambulacral feet Amongst the 
permanently fixed and best-known forms is the 
Pentacrinus Caput -tnedusce, or Medusae -head 
Star of the West Indies. More recently, several 




Pentacrinus Caput-medusse. 

new genera have been discovered, since deep-sea 
exploration and dredging have been suggested and 
carried out, such as Rhizocrinus, which was found 
off the coast of Norway. In Comatula, or the 
Feather-star, the adult form is free, whilst the 
young, which was formerly described as a distinct 
animal, is fixed. The Crinoidea, however, were 
much more abundant during the Carboniferous 
period, where the mountain limestone is largely 
composed of the stalks of the forms that flourished 
there. The individual joints of the stem, when 
separated, are known as St Cuthbert's beads. In 
the Muschelkalk, one of the secondary Triassic 
rocks of Germany, a very pretty form, the 
Encrinus liliformis, or stone-lily, is specially 
abimdant, and is very well known. 

Order 2. The Ophiuridea, represented by 
the 'Sand-stars' {Ophiurd) and 'Brittle-stars' 
{Ophiocoma), are star-fishes having five slender 
arms radiating from a small central disk, on the 
lower surface of which the mouth is placed. The 
arms do not contain any prolongation of the 
viscera, but consist of a central series of ossicles 
united by powerful muscles, and of an external 
mailing of several series of plates of the perison. 
The ambulacral vessel runs along the lower 
surface of the arm, and gives off at each joint a 
pair of long conical tubular appendages, without 
suckers, which are used for locomotion and 
respiration. There is no excretory opening, the 
indigested matter being thrown out from the 
mouth. 

Order 2. Asteroidea. — The common Asterias, 
or Star-fish, which may be taken as the type of 



1 



ZOOLOGY. 




Asterias tessellata (Asteriada). 




this order, is covered with a tough leathery skin 

beset with prickles. 
The animal has 
the form of a star 
with five or more 
rays radiating from 
a central disc. In 
the middle of the 
under surface of 
the disc is situated 
the mouth, open- 
ing into an intes- 
tine, which sends 
prolongations into 
each ray. In some 
forms there is no 
anus present, so 
that the indigest- 
ible portions of the food have to be ejected 
through the mouth, as in the common sea- 
anemone. If the prickly skin be removed, it is 
seen that it is supported by a series of plates, 
beautifully jointed together. On the under sur- 
face of each ray, the plates exhibit a series of 
perforations, through which, in the living state, 
the ambulacra! feet can be protruded. They are 
found in almost all tropical and European seas, 
and some species are found as far north as 
Greenland. 

Order 4. Echinoidea. — The members of this 
order are commonly known as Sea-urchins or Sea- 
eggs. The body is somewhat globose in form, 
and composed of a series of plates jointed to- 
gether. In the Echinus, we 
observe two orifices situated 
at the two poles of this 
globe ; the larger of these 
orifices, directed downwards, 
is the mouth ; at the smaller 
one, placed superiorly, the 
intestine terminates. The 
mouth is furnished with a 
curious apparatus of teeth, 
known as 'Aristotle's Lan- 
tern,' worked by a powerful 
set of muscles attached to 
the edge of the shell near the 
mouth. By the action of the 
teeth the food is ground down 
before it passes into the in- 
testine, which takes a couple of turns round the 
shell before its termination. Round the second 
orifice of the shell are disposed the ovaria, which 
are very largely distended with eggs at some 
seasons, and are eaten under the name of roe of 
the sea-egg. On looking at the Echinoidea in the 
living state, we see that most of them are covered 
with spines of considerable size. Moreover, these 
spines are movable at the base, which is 
hollowed out into a little cup, which fits on a 
rounded projection from the shell, thus forming a 
complete b^-and-socket joint These spines are 
connected to the shell, and are moved by the 
skin which covers the latter. On looking at the 
shell of an Echinus, it is seen to be composed of 
twenty rows of plates, generally hexagonal in 
form, accurately fitted to each other, running 
from pole to pole. They are so arranged that 
there are ten alternating zones, each zone being 
composed of two rows of similar plates. There 
are five double rows of large plates, which are 




Shell of Echinus : 

a, inter-ambulacral plates ; 

b, ambulacral plates. 



imperforate, and studded with tubercles. These 
are the inter-ambulacral areas. The other five 
double rows {ambulacral areas) alternate regu- 
larly with these, and are composed of small 
plates, which are perforated by numerous aper- 
tures for the protrusion of the ambulacral feet. 

These feet aie distended by water admitted 
from without through a specially modified plate, 
called the madreporiform tubercle, which admits 
it into the sand-canal, a straight tube filled with 
peculiarly shaped spicules, which finally opens into 
a ring-like vessel surrounding the oesophagus, and 
sending off tubes in a radiate manner, from which 
the ambulacral feet spring. When water is ad- 
mitted into these feet, they become distended, and 
are protruded through the ambulacral apertures. 
These feet are provided with a small sucker, by 
which they can adhere to the rocks, thus enabling 
the animal to move along. Attached to and 
communicating with the ring-like vessel sur- 
rounding the oesophagus, are two little sacs or 
bags, called Polian vesicles^ which act as reser- 
voirs for the water, so that the ambulacral feet 
can be protruded at will The spines are most 
numerous in the inter-ambulacral areas. In order 
to provide for the growth of the shell, there is 
interposed between adjoining plates a thin mem- 
brane, by the calcification of which the plates 
increase in size at their edges. These animals are 
found on sandy shores, and on the bottom of the 
sea, creeping along with their feet. Their food is 
of a mixed character, consisting of crustacea and 
sea-weed. In some forms, as Spatangus (Heart 
Urchin), the shell is ovoid or heart-shaped, and 
the mouth is eccentric. In these cases, the dental 
apparatus is generally imperfectly developed. 

Order 5. The Holothuridea, the last and most 
highly organised Echinoderms, are destitute of 
spines or prickles, and have the body shaped like 
a cucumber, and inclosed in a highly elastic skin. 
They are commonly known by the name of sea- 
cucumbers. Some of the species are edible, and, 
when dried, are the trepang of commerce. By 
the Malays, they are diligently sought after for the 
supply of the Chinese market 



IV. SUB-KINGDOM ANNULOSA. 

The Annulosa, or Ringed Animals, have their 
segments arranged, one behind the other, from 
before backwards. They exhibit bilateral sym- 
metry, each segment being also symmetrical The 
alimentary canal, which is present in all except a 
few internal parasites, is distinctly shut off fi-om 
the body cavity. In most, a blood-vascular 
system is present, and is always placed dorsally. 
In the higher orders, the nervous system consists 
of a double symmetrical rord, placed along the 
ventral surface of the animal, and having upon 
it small swellings composed of nervous matter, 
and termed ganglia, two ganglia corresponding to 
each segment These gangha give off branches 
to their respective segments. Anteriorly, the 
gullet is surrounded by these nervous cords, 
so that it passes through a ring of nervous 
matter. 

The Annulosa are divided into two principal 
divisions : I. Vermes, and II. Arthropoda. 

139 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



DIVISION I.— VERMES 

(Worms), in which the division of the body into 
longitudinally arranged segments is not apparent, 
or but imperfectly marked ; and there is an 
absence of appendages jointed or articulated to 
the body. 

Class (A). Platyelmia, or Flat-worins, are usu- 
ally flattened and ovoid in form, and the segmen- 
tation of the body is not distinct. The nervous 
system consists of a pair of ganglia, situated at the 
anterior extremity of the body, from which fila- 
ments arise and pass backwards. Some live in 
the interior of other animals, and are parasitic j 
while others are covered with cilia, and swim 
freely in the water. , /■ .1 r 

Order i. C«/<?/V/<rfl— including the family of 
the Taniada, or Tape-worms, which are parasitic 
in the intestinal canal of warm-blooded vertebrata. 
The mature worm is ribbon-like, and consists of 
many joints or segments, which resemble each 
other. The anterior segment, or head, has a circle 
of hooks and suckers by which it is enabled to fix 
itself to the intestinal canal of its ' host' The 
various segments are produced by a process of 
budding from the head posteriorly, so that the 
oldest and most mature are farthest removed from 
it, each new bud being formed between the head 
and the last-formed segment. As neither mouth 
nor digestive system is pres- 
ent, the animal is nourished 
by absorption through the soft 
skin of the body. Running 
down along each side is a 
vessel, which communicates 
with its fellow by a branch at 
the posterior part of each seg- 
ment. This is described as a 
water-vascular system, but in 
none of the Vermes is it ever 
used for purposes of progres- 
sion. Each segment, except 
the head, is provided with 
male and female sexual or- 
gans. The female organ con- 
sists of a branched tree-like 
tube, occupying nearly the 
whole of each segment, which 
_ . , . opens along wth the male duct 

Head, Deck, and upper f., ^ , •,..., . ,. 

joints of Tcenia at the apcx of a little elevation 
solium magnified: placed On the margin or sur- 
V^^b^'lx^. face of the segment. The de- 
of the sucking discs: velopment of these animals 
d, the nedc presents some most remarkable 

phenomena. Sexually mature 
segments can only be formed in the intestinal 
canal of a warm-blooded vertebrate ; but the 
development of an embryo cannot go on unless 
the ova are introduced into the intestinal canal 
of some animal other than the one in which the 
mature segments were produced; so that the 
segments with ova have to be expelled from the 
boweL The joints, after expulsion fi-om the 
bowel, decompose, and liberate the ova, which, 
when swallowed by another warm-blooded verte- 
brate, give rise to an embryo which is provided 
with spines suited for boring. With these it 
perforates the 'wall of the stomach, and reaches 
some solid organ, such as the liver or brain, 

140 



Tape-worm ; 




where it develops for itself a bag or cyst, Jind 
is said to become encysted. In this condition 
it is composed of a 'head' furnished with hook- 
lets, and a vesicle filled with fluid at its poste- 
rior extremity; but it has no generative organs. 
These are the so-called cystic worms, whose 
presence in the brain of sheep gives rise to the 
disease called 'the staggers.' Unless the organ, 
such as the liver or brain, containing these 
cystic worms is swallowed by some other warm- 
blooded vertebrate, they undergo no further 
development. When swallowed, their vesicle 
disappears, and buds are given off from their 
posterior extremity, which develop organs of re- 
production, and constitute the segments of the 
adult worm. The ordinary tape- 
worm met with in the intestinal 
canal of man in this country is 
Tcenia solium, which sometimes 
measures several yards in length. 
The cystic form of this species is 
called Cysticercus celluloses. It 
is found in the muscles of the 
pig, constituting what is known 
as measly pork. If a portion of 
this is eaten by man, the cystic 
form develops itself in his intes- 
tinal canal into a tapeworm. 
Another tape-worm common in 
man is the Tcenia medio-canel- 
lata, which is derived from the 
' measles ' of the ox. Fluke-worm {Dis- 

Order 2. Trematoda — are toma hepaticum). 
parasitic, and include the Dis- 
toma hepaticum, or ' fluke,' which infests the liver 
of sheep, and gives rise in them to the disease 
called 'rot.' The body is flat and oval in form, 
being furnished with two suckers to enable it to 
adhere to its host ^ 

Class (B). Nematelmia, or round-worms, are 
nearly all parasitic and unisexual. The body 
is rounded and elongated, and has an annulated 
appearance. 

Order 3. Gordiacea, or hair-worms, distin- 
guished by their great length, sometimes make 
their appearance in enormous numbers in par- 
ticular places, and give rise to the phenomenon 
of ' worm-showers.' 

Order 4. Nematoda are free or parasitic. 
Type Ascaris lumbricoides, or round-worms of the 
human subject, is elongated 
and cylindrical in form, and 
has a wrinkled appearance. 
An alimentary canal and dis- 
tinct anus are present The 
sexes are distinct The ner- 
vous system is in the form of 
a ring encircling the gullet, 
giving branches forwards and 
backwards. The Thread- 
worms {Oxyuris), which are 
so troublesome to children, 
belong to this group. The 
Guinea-worm {Filaria m^di- 
nensis) hves in the cellular Trichina spiralis spir- 
tissue under the skin chiefly ally coiled within its 
of the legs. It is often several cyst (From Kiichen- 
feet long ; and is common in meister's Parasites.) . 
tropical Africa. 

In the muscles of the human subject, coiled up 




ZOOLOGY. 



within a cyst, has been found the Trichina spi- 
ralis. This parasite has appeared most fre- 
quently in Germany, and its presence is ascribed 
to the use of pork, raw or imperfectly cooked, 
in which the Trichina exists, for it also inhabits 
the muscles of the hog as well as of the human 
being. When thus encysted, it never develops 
sexual organs, but must be again swallowed by 
a warm-blooded vertebrate before it can repro- 
duce itself. Its presence in the muscles gives rise 
to the painful disease called Trichiniasis. The 
non-parasitic forms are represented by the An- 
guillulidce, which are little eel-like worms. One 
species, A. tritici, causes the disease termed 
* cockle' in wheat Another, A. aceti, is met with 
in stale vinegar; whilst a third, A. glutitiis, or 
paste-eel,' is met with in paste that is turning sour. 

Class (C). — Rotifera, or wheel-animalcules, re- 
presented by such forms as Hydatina and Flos- 
cularia, are microscopic aquatic animals, having 
an elongated slightly segmented body, and carry- 
ing at its anterior end a ciliated disc, which, by 
creating a vortex, carries to their mouths any food 
which may be floating in their neighbourhood. 
They possess a mouth and intestinal canal ; and a 
water-vascular system is present. They are very 
tenacious of life ; so that, if they are dried until 
they are quite brittle, on the return of moisture, 
they unfold their wheel-like organs, and are as 
active as before. 

Class (D). — In the Annelida, the segmentation 
of the body is generally distinctly recognisable, 
and all the segments usually resemble each other, 
except those at the two ends. If a segment carries 
lateral appendages, these are never articulated to 
the body. The digestive canal runs straight 
through the animal from the mouth to the anus. 
A system of canals exists, which contain a coloured 
fluid, usually red or green, which is supposed to 
represent the vascular system. The nervous sys- 
tem consists of a double gangliated cord placed 
ventrally, which encircles the gullet anteriorly. 

This class includes two sections : i. Abran- 
£hiata, including the Leeches and Earth-worms, in 
which there is no external respiratory organs or 
branchiae. 2. Branchiata comprises the Tube- 
worms {Tubicola) and the Sand-worms {Erraniia), 
in which branchiae are present. 

Orderi. Discophora—iox example, the leeches, 
which possess an adherent sucker at their an- 
terior and posterior extremities, which they use 
for locomotion. They have no lateral appendages. 
The body has well-marked annulations. They are 
aquatic, living chiefly in fresh water; but a few 
are marine. The mouth of the Medicinal Leech 
{Sanguisuga officinalis) is furnished with teeth 
arranged in a tri-radiate manner. Each tooth has a 
serrated edge, and when the teeth are worked back- 
wards and forwards, they inflict the characteristic 
leech-bite when these animals are applied to the 
skin. Respiration is performed by the skin or by 
involutions of the integument Leeches are her- 
maphrodite, but they are incapable of self-impreg- 
nation. They are very common in the south of 
France, Bohemia, Hungary, and Russia. The 
Horse-leech {Hcemopis sanguisorba) is common 
in Britain ; it is larger than the medicinal leech, 
but its teeth are blunt, and it is useless for medical 
purposes. In Ceylon, the Land-leech is very 



troublesome to men and quadrupeds who have 
occasion to walk, through the grass. They in- 
smuate themselves under the finest stockings, and 




Horse-leech {Hcemopis sanguisorba). 

suck the blood of their victims ; so that the coffee- 
planters are forced to wear leech-gaiters of closely 
woven cloth for protection. 

Order 2. Oligochata-^om^nsc^ the Earth- 
wonns {LumbricidcB). Their organs of locomotion 
consist of a double row of bristles attached to the 
under surface of the body. They are all her- 
maphrodite. The Common Earth-worm {Lumbri- 
cus terrestris) is of great importance to the agri- 
culturist, by continually bringing the deeper por- 
tions of the soil to the surface. Besides they are 
useful as food for birds and fishes, and their value 
as bait is well known to every angler. 

Order 3. Tubicola— zxe all marine, and they 
invariably form for themselves a tube or case into 
which they can retract themselves. This tube 
may be composed of particles of sand, which the 
animal glues together with mucus, as in the genus 
Terebella, or it may be of a homy, or even of a 
calcareous nature, formed from matter excreted 
by the animal. There is no organic connection 
between the tube and its inhabitant, for the crea- 
ture can be easily drawn out of it The organs of 
respiration consist of a tuft of plume-like cihated 
organs situated on the head. These are often 
beautifully coloured, from the coloured fluid, repre- 
senting the blood, which circulates in them. The 
genus Serpula, which forms irregularly twisted 




Serpula contortuplicata. 



calcareous tubes attached to shells and stones, is 
very common along our coasts. 

Order 4. Errantia — are free-swimming anne- 
lids, which do not develop a tube. The seg- 
mentation is distinctly pronounced, and the 
anterior extremity of the body is marked out as 
a head, which is usually provided with eyes. It 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



includes the Arenicola piscatorum, or Lob-worm, 
the Nereis (Sea-centipede), and the Sea-mouse 
(AphrodiU). The respiratory organs are in the 
form of tufts of branchias, which are placed along 
the back or sides of the creature. The back of 
the Sea-mouse is covered by a series of membran- 
ous plates, protecting the bristles of the feet, which 
exhibit beautiful iridescent metallic colours. 

DIVISION II. — ARTHROPODA, 

in which the division of the body into segments is 
well marked, and jointed appendages articulated to 
the body are present. Most of the segments and 
appendages are protected by an outer covering, 
often composed of chitine, which forms a sort of 
exo-skeleton. The appendages are hollow, and 
the muscles are prolonged into their interior. The 
nervous system exhibits the well-marked Annulose 
type. Respiration is performed differently in the 
different groups. The vascular system, when 
present, is always placed dorsally. 

The Arthropoda (Gr. arthros, a joint, zxvd.pous, 
a foot) are divided into four great classes — namely, 
the Crustacea, the Arachnida, the Myriapoda, and 
the Insecta. 

Class i. Crustacea. — In a typical crustacean, 
the body consists of twenty-one segments, seven of 
which belong to the head, seven to the thorax, and 
seven to the abdomen. But sometimes the head 
segments unite with those of the thorax, and form 
a cephalo-thorax. Some of the segments may be 
suppressed. Some or all of the segments are pro- 
vided with a single pair of articulated appendages. 
The animals are fitted for life in water, and they 
therefore breathe by gills, or by the general surface 
of the body. The head carries two pairs of jointed 
antennae or feelers. The appendages for loco- 
motion are borne by the thoracic segments, and 
usually by those of the abdomen also. The body 
is protected by a calcareous or homy covering or 
* crust' They all undergo a series of metamor- 
phoses or changes before they reach the mature 
condition. 

Order i. Ichthyophthira and Rhizocephala, or 
the Parasitica of Lamarck — in their embryonic 
condition are furnished with eyes and antennae, 
and swim freely about ; but the adult is parasitic 
on the eyes and gills of fishes, to which it adheres 
by a suctorial mouth. 
— - Order 2. Cirripe- 

dia (Lat cirrus, a ten- 
dril, and pes, a foot) 
— represented by the 
Acorn-shells and Bar- 
nacles. In the adult 
condition, they are 
permanently fixed, 
and are usually seen 
attached to rocks, 
pieces of floating tim- 
ber, or the bottoms of 
ships. Several of the 
head segments are so 
modified as to form a 
multivalve shell, in- 
closing the animal, 
from which it can 
protrude itself. The thorax is provided with six 
pairs of ciliated limbs, which, being protruded 

113 




Bamade. 



through the opening in the shell, and creating 
currents in the water, bring food to the animal 
The embryo is a free-swimming form, which is 
provided with one eye, has two pairs of antennae, 
and six limbs, which it uses for swimming. In 
the barnacles {Lepadidce), the animal is fixed by 
a long stalk or peduncle ; while the acorn-sheUs 
{Balatii) are sessile, having no stalk. 

Sub-class Entomostraca. — Those crustaceans 
which possess more or fewer than fourteen thor- 
acico-abdominal segments are included under the 
sub-class Entomostraca, which includes five orders. 

Order 3. Ostracoda — for example, the genus 
Cypris, which abounds in every pool of fresh water. 
It is a small animal, protected by a shell com- 
posed of two valves, which it can open and shut at 
wiU. It has two or three pairs of feet, and the 
branchiae or gills are attached to the posterior 
jaws, which surround the mouth. In a fossil state, 
their shells are found abundantly in the Wealden 
rocks of England, in the Carboniferous Lime- 
stones, &c. 

Order 4- Copepoda — for example, Cyclops, one 
of the ' Water-fleas,' which is com- 
mon in all our ponds and ditches. It 
is of small size, and the head and 
thorax are protected above by a 
structure called a carapace. It has a 
single large eye, placed anteriorly, 
and two pairs of antennae. Five pairs 
of feet are present, and are used for 
swimming. 

Order 5, Cladocera — represented 
by Daphnia pulex, another of the 
Water-fleas. The head is distinct, 
and has a single eye, and the remainder of the 
body is inclosed in a shell. 

Order 6. Phyllopoda {phyllon, a leaf, and/tf«j, 
a foot) — includes the genus Apus and the Fairy 
Shrimp, in which the body is protected by a 
carapace. They have always more than sixteen 
feet, which carry the gills ; and the eyes are well 
developed. 

An order, the Trilobita, now entirely extinct, 
was probably allied to the Phyllopoda. The body 
was covered by a chitinous shield, consisting of a 
cephalic shield, a variable number of body-seg- 
ments, and a tail with the joints more or less 
anchylosed, the whole shewing a division into 
three longitudinal lobes, hence the name. The 
eyes were sessile and compound, and the number 
of facets in the lens of one species numbered 6000. 
They were entirely confined to the Palaeozoic 
rocks, and over 200 species have been described 
from the Silurian rocks alone. 




Cyclops vul- 
garis, mag- 
nified. 





Asaphus tuberculatus. 



Limulus Polyphemus. 



Order 7. Xiphosura {xiphos, a sword, and 
oura, a tail) — represented at the present day by 



ZOOLOGY. 




Cyamus Ceti. 



the King Crabs or Molucca Crabs {Limulus), 
which sometimes measure two feet in length. 
The dorsal surface of the cephalo-thorax is covered 
by a large convex shield, upon which are placed 
the eyes. The abdomen is also protected by a 
second shield, which terminates in a long sword- 
like process. The mouth, placed on the under 
surface of the head, is surrounded by six pairs of 
appendages, whose bases are suited for masticat- 
ing food, their extremities being clawed. Attached 
to the abdomen are six pairs of appendages, which 
carry the gills. 

Sub-class Malacostraca includes those crus- 
taceans which have a definite number of body- 
segments. It includes 

DIVISION (a). — EDRIOPHTHALMATA, 

in which the eyes are not situated on stalks, and 
the body is unprotected by a shield. It comprises 
three orders. 

Order 8. Lcemodipoda 
{laimos, the throat, pous, a 
foot). — The head is confluent 
with the first thoracic segment. 
These segments support the 
four anterior feet, so that they 
seem to be under the throat — 
hence the name. The abdomen 
is rudimentary. The most 
common is the Cyamus Ceti 
(or Whale-louse), which is a 
small animal parasitic on the body of the whale. 

Order 9. Amphipoda {amphis, on both sides, 
and pous, a foot). — The respiratory organs are 
attached to the thorax; the abdomen is well 
developed, and composed of seven segments. 
The first thoracic segment is distinct from the 
head, and the thorax carries seven pairs of limbs, 
some of which are directed forwards, some back- 
wards. The species best known in Britain is the 
Talitrus locusta (Sand-hopper), which burrows in 
the sand, and seldom enters the water. 

Order id. Isopoda {isos, equal, and pous, a 
foot). — The head is distinct. The feet are alike, 
and adapted for locomotion and grasping. The 
most familiar is the Oniscus (Wood-louse). 

DIVISION (b). — PODOPHTHALMIA. 

The eyes are supported on movable stalks, and 
the cephalo-thorax is protected by a carapace. It 
includes two orders. 

Order ii. Stomapoda {stoma, a mouth, and 
pous, a foot). — They are all marine. The Locust- 
shrimp {Squilla), which is common in the Medi- 
terranean, is a well-known form, and is about 
seven inches long. The gills are naked, and 
adhere to five pairs of feet, which are abdominal 
in position, and leaf-like in form. Some of the 
anterior appendages are transformed into power- 
ful, prehensile feet, but they are never used for 
nipping, while the posterior feet are used for 
swimming. 

Order 12. Decapoda {deka, ten, pous, a foot). — 
It includes the stalked-eyed crustaceans, whose 
cephalo-thorax is protected by a strong calcareous 
carapace, which exhibits no trace of segmentary 
division. The gills lie in a cavity on each side of 
the cephalo-thorax. The thoracic legs are ten in 
number, hence the name It includes a gpreat 




number of species, most of which are useful for 
food, and they are by far the most highly organ- 
ised of all the Crustaceans. According to the 
development of the abdomen, three sub-orders are 
formed. 

Sub-order i. Macrura {makros, long, oura, a 
tail), or Long-tailed Decapods— including the 
Lobster, Prawn, Cray-fish, and Shrimp. The 
abdomen is well developed, and ends in a powerful 
fan-shaped swimming organ. The head carries 
the compound eyes, placed on long movable 
stalks. Two pairs of antennae are also present 
The mouth is on the under surface of the head, 
and some of the appendages are so modified as 
to form powerful claws or nipping organs. The 
abdominal segments carry swimming organs. The 
heart is well developed, and is situated dorsally. 
The nervous system is well pronounced, and is 
situated ventrally. 

Sub-order 2. Anomura (anomos, irregular, and 
oura, a tail). — The abdomen is not so long as in 
the Macrura, nor so short 
as in the next order. To 
this order belongs the 
Hermit Crab iPagurus), 
whose abdomen is quite 
soft. They are remark- 
able for living in the 
deserted shells of mol- 
lusca, exchanging a less 
for a larger as they in- 
crease in size. It fixes 
itself in the shell by a 
sucker and rudimentary 
feet. Well-developed feet 
are present, the anterior 
pair being usually trans- 
formed into formidable nippers. They feed upon 
dead fish. When alarmed, they retire within the 
shell, and close the aperture with their claws. 

Sub-order 3. Brachyura {brachys, short, oura, a 
tail), or Short-tailed Decapods — have the tail 
short, and folded under the large cephalo-thorax. 
The Large Edible Crab {Cancer pagurus) is the 
type. The legs are of moderate length, but the 
claws are large. At low tide in summer, it is 
found in holes of rocks. The Small Edible Crab 
{Carcinus mcenas) is another well-known British 
Species. The Land-crabs (G^^fam««j')— called also 
violet crabs and white crabs, from their colour — 
are natives of the West India Islands and South 
America. They have an arrangement of leaflets 
for retaining moisture for their gills. They live in 
mountainous places, far from the sea, which they 
visit once a year to deposit their eggs. During the 
day, they retire into their burrows, which they make 
in the earth, roaming about at night in search of 
food. The Common Crab, on coming out of the 
e.'gg, has a long tail, with several curious spine- 
like processes attached to it, and was formerly 
described as a distinct animal under the name of 
Zoea. It undergoes curious metamorphoses before 
it reaches the adult condition. 

Class 2. Arachnida — are annulose animals, 
whose respiration is aerial. The head is con- 
fluent with the chest, thus forming acephalo-thorax, 
and the abdomen never carries jointed append- 
ages. Eight legs are present, but the antennae as 
such are absent. It includes the familiar group 

of Spiders and their allies. 

^ lit 



Hermit Crab in shelL 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Sub-division (A). Trachearia {trachea^ the wind- 
pipe) — includes such spiders as breathe by tracheae. 
These tracheae are tubes which ramify through 
the tissues of the body, and open on the surface 
by distinct ap)ertures called sttgmata. The tubes 
are kept pervious by a spiral elastic filament, 
which is coiled up within them. The Trachearia 
have never more than four eyes. 

Order i. Podosiomaiti.— They are all marine, 
and are commonly known as ' Sea-spiders.' Some 
of them, as Nympha^ are found amongst the 
stones and weeds on the sea-shore, while others, 
such as PycruogoHum are parasitic upon fish and 
other marine animals. 

Order 2. Acarina, or MoHomerosomaia {monos, 
one, tturos, a part, and soma^ the body) — in- 
cluding the Mites and Ticks. The body con- 
sists of a roundish mass, exhibiting no trace 
of segmentation. They breathe by tracheae. 
The family of the Unguatulina is remarkable 
in that, in their adult condition, the characters 
of the order are not easily traced, but the young, 
when still in the egg, are furnished with four 
pairs of jointed legs. The Unguatulina are 
found in the lungs of some of the mammalia. 
The family of the Macrobiotida are microscopic, 
and are known by the name of Sloth or Bear 
Animalcules. Their favourite habitat is under the 
gutters of houses. They resemble the Rotiferae 
in so far as, though dried for a considerable time, 
they return to life the moment they are moistened. 
But the most familiar of all is the family of the 
Acarida, including the Cheese- 
mite, which has four pairs of 
legs, and uses them for walk- 
ing. The Sarcoptes scabiei 
produces, by burrowing under 
the skin, the disease called 
* itch.' The Hydrachnidce, or 
water- mites, have their legs 
fringed, and swim about in water. The Ticks 
{Jxodts) have a ' rostrum,' which enables them to 
penetrate and attach themselves to the skin of 
their host, generally one of the beetles. 

Order 3. Adelarthrosomata. — The abdomen is 
anited to the cephalo-thorax, but it is always more 
or less distinctly segmented. The mouth is armed 
with jaws, and the tracheae open by two or four 
openings on the imder surface of the body. To 
this order belong the family of the Phalangida, 
or Harvest-spiders, characterised by the enormous 
length of their legs, which resemble stilts. The 
family of the Cheliferida includes the Book-scor- 
pion, whose palpi are long, and terminated by 
long nipp>ers like those of the scorpion. Their 
favourite habitat is amongst old books. 

Sub-division (B). P^/wz^^war/Vr.— These breathe 
by pulmonary sacs, which are involutions of the 
integument, opening on the surface of the body 
by stigmata, which lead into a blind chamber. 
They have six or more simple eyes. The Pulmo- 
naria comprise two orders. 

Order i. Pedipalpi — in which the abdomen is 
distinctly segmented, and attached to the cephalo- 
thorax. This order includes the family of the 
Scorpionidte — which are amongst the largest 
and best known of the Arachnida. They have an 
elongated abdomen, armed at its extremity with a 
short curved claw. It is with this organ that the 
Scorpion inflicts its sting, which is doubtless very 

144 




Acarus (Mite). 



disagreeable, and often attended with troublesome 
symptoms, Uiough its danger, to man at least, 
seems to have been overrated. The maxillary 

{)alpi are very large, and form prehensile organs 
ike the claws of a lobster. With these they seize 
their prey, strike it with the sting, and then devour 
it. They have four. pairs of stigmata opening on 
the imder side of the abdomen. It is in the tropics 
that the Scorpions attain their largest develop- 
ment. 

Order 2. Dimerosomata (Gr. di, two, meros, 
a part, and soma, a body) includes the true 
Spiders. The head and thorax are united into a 
single mass, and the abdomen is soft and unseg- 
mented, being separated from the cephalo-thorax 
by a slight constriction. The head carries six or 
eight simple eyes. The mandibles are large, and 
perforated by the duct of a gland, which secretes a 
poisonous fluid. The palpi are never chelate 
or clawed. The pulmonary sacs are two or four 
in number, and open on the under surface of 
the abdomen. Tracheae may also be present. 
But by far the most remarkable organs are the 
spinnerets, by means of which these animals spin 
their curious and beautiful webs for intercepting 
the prey upon which they expect to feed, or for 
lining their abodes. The spinnerets are teat-like 







mWu M 



J 



Spider, with thread-making organ magnified. 

organs, four or six in number ; they are per- 
forated at the apex by minute openings placed 
on the under surface of the abdomen. The sub- 
stance composing the web is secreted by glands 
placed close to the spinnerets. It is viscid at first, 
and passes through the spinnerets, which give it 
its proper thread-like shape, becoming hard on 
exposure to the air. The Argyroneta aquatica, 
or Diving-spider, weaves for itself a bell-shaped 
cell, at the bottom of the water, to which it retires 
to devour its prey. It carries down air by entang- 
ling it amongst the hairs which cover its body. 
All spiders are predaceous, but some do not 
construct a web for the capture of their prey, 
such as the Tarantula {Lycosa tarantula) of 
Southern Europe, which springs suddenly upon 
its unwary victim. The Mygale, the most power- 
ful of the spider order, when at rest, covers a 
space of six or seven inches in diameter. Other 
species are called Mining-spiders, because they 
construct their habitations in the ground, lining 
them with their silk-like secretion. The Aranea 
domestica (Common House-spider) is well known. 
The maxillary palpi of the male spider are speci- 
ally constructed for bringing the male into contact 



ZOOLOGY. 




Lithobius forcipatus. 



with the female element in the process of repro- 
duction. Spiders are oviparous, but undergo no 
metamorphoses. 

Class 3. Myriapoda have the head distinct, 
bearing a pair of antennae, and usually a number 
of simple eyes. The thorax is united with the 
abdomen, the whole being divided into a large 
number of similar segments, each furnished with 
one or two legs on each side. They respire by 
tracheae. 

Order i. Chilopoda, in which the number of 
joints composing the antennae is never less than 

fourteen. Litho- 
bius forcipatus, a 
British species, is 
about two inches 
in length, and 
quite harmless ; 
but some of the 
Scolopendra, well 
known as Centipedes, found in hot climates, are 
powerful and predaceous, and sometimes measure 
one foot in length. 

Order 2. Chilognatha, in which the antennae 
are composed of only seven joints. It includes 
the vegetable-eating Millepedes {lulus), charac- 
terised by the great number of the legs. The 
familiar Gally-worm {Polydesmus) is another ex- 
ample. 

Class 4. Insecta — are articulate animals, in 
which the body is divided into three distinct 
regions — the head, thorax, and abdomen. The 
head carries the antennae or feelers ; the legs, 
six in number, being borne by the thorax ; while 
the abdomen is destitute of jointed appendages. 
They breathe by tracheae, and are generally fur- 
nished with wings attached to the thorax. 

Considering the vast number and variety of 
insects that are found everywhere upon the earth, 
with their diversity of habits and structure, it must 
suffice here to point out the main characters of the 
class, merely mentioning some of the most im- 
portant families. Indeed, the subject is so vast, 
that it is studied as a distinct branch of Zoology, 
under the term Ento7nology. 

The body is never composed of more than 
twenty segments, which have usually a horny or 
chitinous investment, forming an exo-skeleton, to 
which the muscles are attached. The segments 
are united to each other by a membranous skin, 
thus giving flexibility to the whole. The seg- 
ments of the head are united into a single piece, 
which bears the antennae, the eyes, and organs of 
the mouth. The mouth is variously modified, ac- 
cording as it is suited for biting, for suction, or for 
both combined. In Masticat- 
ing or Biting insects, such as 
Beetles, the mouth consists of 
six separate organs (see fig.), 
(i) An upper hp (labrum, /i) 
attached to the under surface 
of the head ; (2) A pair of 
horny biting jaws (mandibles, 
mni) ; (3) A pair of chewing 
jaws (maxillae, inx), bearing 
one or more pairs of 'maxil- 
lary palpi' {ffip)', and a lower 
lip (labium, /2) also bearing a 
The typical suctorial mouth, 




Mouth of a Beetle. 



pair of palpi {Ip), 
10 



as seen in the Butterflies, consists of a long 
trunk, which, when at rest, is coiled up in a 
spiral form beneath the head. It represents the 
maxillae, which, coming together, form a tube, 
through which the juices of the flowers are sucked 
up. The maxillary palpi are very small, and the 
labrum and mandibles are rudimentary. The 
labium, though very minute, bears two large 
palpi, forming the hairy cushions between which 
the tnmk is coiled up when at rest. In the Bee, 
the parts are modified partly for biting, and 
partly for suction. The labium and maxillae are 
elongated, the latter constituting a sheath which 
incloses the elongated tongue, thus forming a 
tubular organ, quite incapable of being coiled up, 
and through which fluid nutriment is sucked. 
The mandibles and labium retain their ordinary 
form. In Bugs and their allies, the labium forms 
an elongated tubular sheath, inclosing four bristle- 
shaped organs, which are the modified mandibles 
and maxillce. The labium of the House-fly is 
lengthened and grooved on its upper surface. 
This groove receives the modified mandibles and 
maxillae in the form of bristles and lancets, which 
are used for penetrating the skin and sucking the 
blood of other animals. 

The thorax is composed of three segments, 
which are named from before backwards, pro- 
thorax, meso-thorax, and vieta-thorax. Each 
of these bears a pair of jointed legs. The latter 
two segments also usually carry a pair of wings 
each. The legs are composed of several joints, 
named the coxa, trochanter, femur, and trasus. 
The wings are variously modified in the different 
orders, and consist of a double membrane, which 
is supported by hollow tubes or ' nervures,' which 
ramify in every direction, and contain processes 
of the tracheae, and passages for the circulation. 
The abdomen is composed typically of nine seg- 
ments, though these never carry legs. Some 
appendages connected with the generative function, 
or for leaping, for offence or defence, may, how- 
ever, be connected with it. The digestive systetn 
in insects consists of a mouth leading into a gullet, 
which opens into a ' crop.' From this, in Mas- 
ticating Insects, it leads into a ' gizzard,' furnished 
with horny plates. This gizzard leads into the 
true stomach, continued into the intestine, which 
terminates in a 'cloaca,' common to it and the 
generative organs. Salivary and other glands are 
present, but no absorbent system. The heart is 
placed dorsally, and consists of several sacs, which 
open into each other from behind forwards. The 
circulating fluid enters at the posterior extremity 
of the so-called ' dorsal- vessel,' and is propelled 
forwards by it, escaping anteriorly, and passing 
amongst the tissues, and, as it were, bathing them, 
for no true veins or arteries have been detected 
in the bodies of insects. In its course it is aerated 
by being exposed to the air contained in the 
tracheae, which ramify throughout the body. The 
nervous system exhibits the typical annulose 
plan, and is placed ventrally. The eyes are 
usually compound — that is, they consist of multi- 
tudes of simple eyes, each of which receives a 
nervous twig. The eye of the house-fly has four 
thousand of these simple eyes. Insects are dis- 
tinguished beyond all other animals by their 
powers of locomotion, and the perfection of 
their instinctive actions. The antennae seem 
to be organs of touch. Insects are unisexual. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



and most are oviparous. Many insects undergo 
changes of form {metamorphosis) in their de- 
velopment from the immature to the adult con- 
dition. Those which do not undergo this change 
are called Ametabolic Insects (Gr. a, without, 
metabole, change). The young of these insects 
resemble their parents m all respects except 
in size; moreover, they are destitute of wings. 
Those which only undergo a half-metamorphosis 
are called HemimetaboUc Insects. They undergo 
three stages. The young is termed larva; in the 
second stage it is fiupaj and in the third, the 
perfect insect or imago. The larva differs from 
the imago in its smaller size, and in the absence of 
wings, while the pupa differs from it only in the 
wings being rudunentary. This metamorphosis 
is said to l^ incomplete. Those which undergo 
a complete metamorphosis are called Holometa- 
bolic Insects. The larva is worm-like, feeding 
voraciously, and growing rapidly. It is then called 
caterpillar or grub. After frequently changing its 
skin, it passes into the pupa or chrysalis state, 
when it becomes incased by a coriaceous covering, 
and seems all but devoid of life. Other larvas spin 
for themselves a protective covering, which sur- 
rounds the chrysalis, and is termed the ' cocoon ' 
(the Silkworm), while others reside in tubes con- 
structed by themselves (the Caddis-worni). Finally, 
it emerges from this condition as the imago, or 
perfect insect, with fully developed wings, ready 
for flight 

Sub-class i. Ametabola. — The young pass 
through no metamorphosis ; imago destitute of 
wings ; eyes, if present, are simple. It includes 
three orders. 

Order i. Anoplura — are typified by the Com- 
mon Louse (Pediculus), a creature justly regarded 
with loathing, because it never exists unless in 
connection with dirty habits. The head bears t\vo 
simple eyes and a suctorial mouth. They are all 
parasitic on mammiferous animals — man, the dog, 
and sheep having each an appropriate parasite of 
this order. 

Order 2. Mallophaga — are specially common 
on birds, hence called Bird-lice. Their mouth is 
suited for biting, and they live on the more delicate 
portions of the feathers. 

Order 3. Thysanura — 
includes the Podura, or 
Spring - tails, which pos- 
sess a forked tail, curved 
under the animal, by sud- 
denly extending which, 
they are enabled to spring 
to a considerable distance. 
Sub-class ii. Hemimetabola—m. which the 
metamorphosis is incomplete. This sub -class 
includes three orders. 

Order 4. Hemiptera {hemi, half, pteron, wing). 
— Mouth suctorial, the labial palpi forming a 
sheath for the style-like maxillae and mandibles, 
and thus protecting them. With these bristles, 
the insect pierces tiie plants or animals upon the 
juices of which it feeds. The head bears a pair of 
compound eyes, and usually also several simple 
eyes. Most of them possess four wings. This 
order is subdivided into 

Sub-order (A). Homoptera {homos, like, and 
pteron, a wing) — in which the anterior pair of 
wings are of similar consistence throughout, often 
somewhat parchmenty, and the mouth looks 

146 




Podura villosa. 



backwards, so that the rostrum springy from the 
back of the head. These are represented by the 
Coccidce (Blight Insects) — for example, the Coccus 
cacti (Cochineal Insect), esteemed for the splendid 
colour it furnishes. It takes seventy thousand of 
these insects to make a pound of cochineaL An 
East Indian species {Coccus laced) yields shell-lac 
and lac-dye. In these cases, it is only the female 
insect that yields the colouring matter. The 
Aphides (Plant-lice) inhabit trees or plants, to 
which they prove highly destructive, feeding, as 
they do, upon the juices they contain. They ex- 
hibit some very peculiar phenomena in their 




Fulgora latemaria. 

manner of reproduction. The Fulgora latemaria 
(Lantern-fly of Guiana), in which the forehead is 
much prolonged, is said to emit light in the dark. 
The Aphrophora spumaria, or Frog-hopper, a 
British species, also belongs to this group. Its 
larva envelops itself in a frothy secretion, which 
has received the name of ' cuckoo-spit.' The 
Cicada was celebrated by the Greek poets for its 
fine song, peculiar to the male, and produced by 
the vibration of a drum-like organ situated at the 
side of the abdomen. 

Sub-order (B). Heteroptera, or Bugs {heteros, 
different, pteron, a wing) — in which the wings are 
chitinous towards the base, and membranous 
towards the point, the beak springing from the front 
of the head. The Boat-flies or Water-bugs {Nolo- 
nectd) haunt the surface of still waters. They use 
their hind oar-like feet for swimming, and with 
their anterior pair they seize their prey. The 
Nepidce (Water-scorpions) are fierce insects, and 
lurk in ponds, living solely on insects. The Cimi' 
cidcB (Bugs) are unhappily familiar to us, by their 
intrusion into our bed-chambers. When irritated, 
they emit an offensive odour. 

I . Order 5. Orthoptera {orthos, straight, pteron, 
a. wing). The mouth is admirably suited for bit- 
I ing ; wings four, the anterior pair of a leathery tex- 
! ture, and forming a protection for the posterior, 
I which are larger, and folded in a fan-like form. 
I This order contains two sections. The first of 
these sections, the Saltatoria, are all herbivorous 
insects, and have the hind-legs elongated, and 
I fitted for leaping. It includes the family of the 
! Locustina (Locusts), so common in warm climates. 
j * Wherever they alight, all signs of vegetation dis- 
appear, and cultivated grounds are left a desert' 
The most common species is the Locusta migra- 
' toria, which is so formidable an enemy to agri- 
I culture in Southern Europe, and even reaches our 
own island. The Gryllina (Grasshoppers) have 
very long antennae, and the largest British species 
I is the Gryllus viridissimus, measuring about two 
inches in length. They are so pugnacious that if 
two are put into a box, they almost invariably 
fight, and the victor dines off the legs of the 
vanquished. The other British species are all of 



ZOOLOGY. 



small size. These are the little chirpers which 
we hear on heaths and sunny banks. The A chetida 




\ 



Female Grasshopper (Gryllus viridissimus). 

(Cricket family) are a very noisy race; for the 
chirping of the House-cricket {Acheta domestica), 
produced by the rubbing of the elytra-cases against 
each other, can be heard at a considerable dis- 
tance. The Field-cricket {A. campestris) and 
Mole-cricket [Gryllotalpa vulgaris) also belong to 
this family. The section Cursoria have the legs 
long, and suited for running. The Mantina have 
the fore-legs converted into powerful raptorial 
organs. They are carnivorous, and very pugna- 
cious. The Chinese amuse themselves with their 
combats, keeping them for this purpose in cages. 
The Blattina (Cockroaches) are nocturnal insects, 
which infest kitchens and bakehouses. The 
Common Cockroach {Blatta orientalis) is too well 
known to require description. The Forficulida 
■ (Ear-wigs) are likewise placed in this section. 

Order 6. Neuroptera (Nerve-wing) — have four 
membranous wings, which are reticulated or inter- 
laced with a delicate network of fine nervures. 
Metamorphosis in some is complete, though in 
most it is incomplete. The Libellulidce (Dragon- 
flies) are slender in form, and beautiful and varied 
in their colouring, though very voracious in their 
habits. They have four large, nearly equal retic- 
ulated wings, and a powerful masticatory apparatus. 
Their larvae and pupze inhabit the water. The 
EphemeridcB (May-flies), also called Day-flies, from 
the short duration of their life in the perfect state, 
are found, during autumn and summer, in every 




May-fly {Ephemera vulgaUi) — Larva, Pupa, and Imago. 

I^brook and pond. The Termitidce (White Ants) 
ire social insects, living in vast communities, 
md chiefly confined to warm climates. They con- 
struct most beautiful habitations either on the 
round or on trees, and assist in the removal 
>f dead and decomposing organic matter. The 
\ MyrmeleontidcB or Aiit-lions, whose larvae are so 
I -destructive to ants, live, in the perfect state, upon 
*ie nectar of flowers. The larvae entrap their 



prey by excavating conical pits in sandy places, 
at the bottom of which they conceal themselves 
entirely, with the exception of the head and power- 
ful jaws. When an unfortunate ant or other insect 
falls into this pit-fall, it is soon devoured by the 
voracious myrmelio. 

Sub-class hi. Metabola— in which the meta- 
morphosis is * complete.' It includes six orders. 

Order 7. Aphaniitera — includes the Common 
Flea {Pulex irritans). The wings are rudimentary, 
and represented by four scales. The mouth is 
suctorial, and its power to penetrate the human 
skin, for gastronomic purposes, is too well known. 

Order 8. Diptera — have only a single pair of 
wings developed — namely, the anterior ; the pos- 
terior pair being rudimentary, and representea by 
organs called ' halteres ' or ' balancers.' The mouth 
is suctorial The HippoboscidcB (Horse-flies or 
Forest-flies) are parasitic upon other animals. 
Hippobosca equina infests the horse, and Melo- 
phagus ovinus is the Sheep-tick. Amongst the 
MuscidcB, or Flies, the most familiar species is the 
Musca domestica (House-fly), whose larvae are bred 
in manure, and undergo their change in a few days. 
Their purpose is to consume substances which would 
taint the atmosphere. They possess the power 
of flying backward. The TabanidcB or Gad-flies 
have a suctorial mouth, provided with six lancets, 
with which they pierce the skin of their victim. 
The Cleg {Tabanus pltivialis) is familiar to most 
of us. Many of the Tipulidce (Water-spinners), in 
their larval condition, are very destructive to the 
roots of grass and to wheat-crops. The CulicidcB 




Gnat, magnified : 

I insect depositing eggs; 2, insect escaping from pupa cas«; 

3, larva of gnat ; 4, floating raft of eggs. 

(Gnats) are specially blood-thirsty, and the dis- 
agreeable effects of their bite are freq^uently enough 
experienced. Their larvae are aquatic. The Mos- 
quitoes of warm climates interfere so much with 
our ease and comfort as to become one of the 
worst of pests. The Midge, so well known for its 
aerial dances, is the smallest species of the family. 
Order 9. Lepidoptera (Gr. scaly -winged),. 
Moths and Butterflies.— The structure of the 
mouth has been described already. The wings, 
four in number, are covered by minute scales, 
which are implanted on the membrane of the 
wing like the tiles on a roof. The beautiful 
metallic colouring which occurs in many species 
of this order is not due to the presence of pig- 
ment, but is owing to these minute scales having' 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



upon them numerous delicate striae, which break 
up the rays of light, and so cause the iridescent 
appearance. The Upidoptera feed upon fluid 
nutriment. The larvas are know-n as Caterpillars, 
which have a masticator)' mouth ; and when they 
attain their full size, they spin around their bodies 
a case or cocoon of silk, in which to spend their 
life as a pupa or chrysalis. From one species 
we derive the silk which is woven into one of 
the most elegant kinds of cloth. The glutinous 
matter of which the threads are composed is 
secreted by glands analogous to the salivary 
glands. It is forced through a small opening at 
the end of the lip, and hardens as it is exposed to 
the air. Some species, however, form no cocoon, 




Aigynnis Paphia. 

but hang in the pupa state from some lofty place. 
At the proper time, the perfect insect bursts from 
its case, to spend a brief, gay existence in the air, 
to lay its eggs, and then perish. 

Family PapilionicUz (Butterflies) are also called 
Diurna, because they fly about during the day, 
and are distinguished by the extraordinaiy beauty 
and variety of the colours which adorn their wings. 
Their antennae are almost always terminated by a 
knob. Over 2000 species exist in Great Britain 
alone ; but it is in tropical climates where these 
most beautiful of all insects attain their greatest 
size, and exhibit the greatest variety of absolutely 
dazzling hues. 

Family Sphingida (Hawk Moths), or Crepuscu- 
laria, so called from their general habit of flying 
abroad at twilight Their colour is duller than 
the butterflies, and when flying, they make a 
humming noise. The Death's-head Moth [Acher- 
ontia atropos) has a skull-shaped patch of colour 
on the back of the thorax, and its sudden appear- 
rance has been regarded as an evil omen. 

Family Noctuina, or Moths Proper, fly only by 
night, and are of a dull style of colouring. This 
family includes the Silkworm {Bombyx mori), a 
native of China. It was imported into Europe in 
the reign of the Emperor Justinian, in 550 a.d. 
The caterpillar of the silkworm, when it has 
attained its full size — three inches long — and be- 
fore it passes into the chrysalis stage, spins for itself 
an oval ball or cocoon composed of a long slender 
filament of yellow silk. After emancipating itself 
from its silken prison, it seeks its mate. In two 
to three days afterwards, the female having depos- 
ited her eggs, from 300 to 400 in number, both 
insects terminate their existence. 

Order 10. tlymenoptera (or Membrane-winged) 
—in which the wings are four in number, of a mem- 

148 



branous texture, with few nervures, the anterior 
being larger than the posterior pair ; they are 
sometimes absent Mandibles are always present,, 
and the arrangement of maxiUae and labium into 
a suctorial organ has been described aheady. 
The females are furnished at the extremity of the 
abdomen with an ovipositor, and in some species 
(Bees, Wasps) this organ is modified, so as to 
constitute a most formidable offensive weapon. 
Many possess instinct of a very high degree, and 
some live in social communities, as the Bees and 
Ants. This order includes the following families : 

TenthredinidcB (Saw-flies). The females have 
an ovipositor which combines the properties of a 
saw and a file. With this, they bore a series of 
holes in trees, depositing in each an egg, with a 
drop of frothy liquid, which seals up the hole. 
The larvEe have from ten to sixteen feet, and so 
are easily distinguished from the caterpillars of the 
Lepidoptera, which they resemble. 

Ichneumonidce (Ichneumons). These are para- 
sitic, and insert their sting into and deposit their 
eggs in the larvae of other insects, where the 
young, when hatched, find sufficient nourishment 
The grub ultimately falls a victim to its ravages ;: 
though they carefully avoid injuring the vital parts 
of the larva on which they prey. Scarcely an in- 
sect exists which in the larval stage is exempt 
from attacks from one or other species of this 
family, so numerous are they. 

CynipsidcB (Gall-flies). These insects deposit 
their ova in living trees, and by their presence 
give rise to the formation of excrescences, called 
galls, such as those on the leaves of the oak-tree. 
The larvae feed on the interior of their habitations, 
where they remain for five or six months. Some 
undergo their metamorphoses within the galls, but 
others escape through small apertures to undergo 
that change. Galls are imported from the Levant, 
and are used in the manufacture of writing-ink 
and dye-stuffs. 

Formicidce (Ants), so celebrated for their in- 
dustry, live in societies, often of great extent, 
consisting of three distinct kinds of 
individuals — males, females, and neu- js\x-<^ 
ters. The males are winged during . >osp^^ 
the whole of their existence, the females rXV 
during only part of their mature state. / ™ ^ 
At a certain period in summer, the j^gy^er Ant 
males and females appear in large (Worker), 
quantities, quit the nest, and copulate 
in the air, when the males speedily die. The 
females then lose their wings, fall to the ground, 
and are picked up and carried to the nest by 
the neuters, when they become the queens of 
future societies. The neuters form the great 
bulk of the community, and upon them depends 
the entire labour of the community. They are 
really females in which the sexual organs are un- 
developed from the difference of food in the larval 
stage. They construct the nest, and attend upon 
and feed the young larvae. Like the females, 
they possess a sting. The larvae of ants, unlike 
those of bees, are never inclosed in cells. The 
food of most species of ants consists chiefly of 
aphides or plant-lice. Some species in India 
and in the south of Europe hoard grain and 
other seeds. The nests of ants consist of numer- 
ous chambers communicating by winding and 
tortuous passages, and they are sometimes exca- 
vated in Uie ground, at other times in the trunks 



ZOOLOGY. 



of old trees. Some ants, as Formica rufescens^ 
have the very peculiar instinct of capturing the 
pupae of other ants and making slaves of them. 
Ants have another very strange habit — namely, 
that of milking the aphides or plant-lice. These 
aphides excrete a saccharine substance, or honey- 
dew, of which the ants are extremely fond. To 
obtain this, the ant pats the abdomen of the 
aphis with its antennae, and when the drop has 
been obtained, it passes on to another aphis. 

Vespidce (Wasps) generally form large com- 
munities, composed of males, females, and neuters. 
A colony is commenced in spring by young 
females which have lain dormant during the 
winter, when they set about building a nest, in 
which they lay eggs, and attend to the larvae. 
The first brood consists of workers, upon whom 
ultimately depends the work of the community. 
The nest is made of a paper-like pulp, made by 
masticating and moistening the wood or bark of 
a tree. 

Of the Apidce, or Bees, some are solitary, while 
others live in detached communities, under the 
apparent rule of an individual. Amongst Social 
Bees, such as the Humble and Hive Bees, only 
one in each hive is a true female, distinguished by 
her size, and called the queen. About six hundred 
are males, usually called drones, and the remainder, 
about fifteen thousand, are neuters, destined for 
labour. The queen, in the larval state, is fur- 
nished with a cell of royal dimensions, and is 
supplied with the most nutritious and delicate 
kind of food. In due time, she comes forth in 
all the dignity of majestic size and full colouring. 
The neuters are placed in six-sided cells, so pro- 
portioned as to limit their growth, and prevent 
their full development. They are fed on simple 
fare. The males exist only between April and 
August, when they are destroyed by the workers. 
The cells are six-sided, and are so constructed 
as to yield at the same time the least expenditure 
of material with the greatest strength ; the instinct 
of an insect thus coming to the very same result 
as the highest human intelligence. In some cells, 
honey is stored up, and in others the eggs are 
laid. The eggs from which perfect females or 
queens are to be produced are laid in cells much 
larger than the rest, and of different forms. The 
drones are killed at the end of summer, but the 
queen and the workers remain ; and when the 
hive is over-peopled, colonies are sent forth with 
young queens in search of another habitation. 

The Solitary Bees present great variety of habit, 
some, such as the Carpenter Bees (Xylocopd), 
making their nests in old wood ; the Mason Bees 
{Osmia) construct their nests by gluing together 
grains of sand ; while the Cuckoo Bees {NotnadcE) 
build no nest at all, but deposit their eggs in the 
nest of other species. 

Order ii. Strepsiptera — are parasitic in the 
interior of Bees and Wasps. The females have no 
wings, but the males have a pair — the posterior — 
X)f large membranous wings, folded longitudinally. 
Neither the jaws nor the anterior pair of wings 
are developed. 

Order 12. The Coleoptera {koleo, a sheath, 
id pteron, a wing), or Beetles, have the anterior 
pair of wings horny or chitinous, and forming a 
protective covering (elytra) for the posterior pair. 

"le mouth is masticatory, and possesses both 
landibles and maxillas. The metamorphosis is 



complete, and the pupa is inactive. They are the 
most numerous and best known of all the orders 
of insects. 

The primary division of Beetles is founded 
upon the number of joints in the divisions of their 
feet or tarsi. 

Sectio7i Trimera, or beetles which have only 
three joints in their tarsi. The Two-spotted Lady- 
bird {Coccinella bi-punctata), so called from having 
two spots on its elytra, is an example. Its larvae 
feed upon aphides, so that these insects ought to 
be encouraged, and they are of great use to land- 
owners by devouring the aphides which swarm on 
hops. 

Sectioft Tetramera contains such beetles as 
have four joints in each foot. They all feed upon 
vegetable substances. It includes the Weevils 
{Curculionidts), which have the anterior part of 
the head extended into a kind of muzzle. They 
are dangerous enemies to our vegetable stores. 
The Xylophagi, or Wood-eaters, are small in size, 
but exceedingly numerous, and do almost in- 
credible mischief to mankind. The Longicornes, 
distinguished by the length of their antennas, in 
their larval state bore deep tunnels into trees. 

Section Heteromera, which have five articula- 
tions in the first four tarsi, and only four in the 
hindmost pair. They are terrestrial in their habits, 
live chiefly in dark places, and feed upon vege- 
table substances. The Churchyard Beetle {Blaps 
mortisagd), found in dark and dirty places about 
houses, is a well-known example. The larva of 
Tenebrio molitor is known as the Meal-worm. 
The TrachelidcB have the head supported on a 
pedicle or neck. Example — Lytta vesicatoria 
(Blister-fly) is very common in Spain, and hence 
the common name, Spanish-fly. The beetles are 
shaken from the trees, and collected in sheets 
spread upon the ground, and are killed by ex- 
posure to the fumes of vinegar. 

Sectiofi Pentamera. — The majority of insects in 
this section have five joints in the tarsi. It 
includes several families — for example : 

The vast family of the Lajnellicornes have the 
antennae club-shaped, composed of thin plates 
arranged like the leaves of a book, which they 
can open or shut at pleasure. They are entirely 
vegetable feeders, and vary much in form, colour, 
and size. The Cetonia aurata (Rose-beetle) may 
be taken as the type. It includes also the sacred 
Egyptian Beetle {Ateuchus sacer), which was con- 
secrated to the sun, and therefore regarded as 
an emblem of fertility ; the Stag-beetle (JLucanus 
cervus) ; and the Cockchafer {Melolantha vul- 
garis). The Dynastes Hercules^ a native of Brazil, 




Dynastes Hercules. 

sometimes attains a length of five inches. It has 
a horn projecting from the head, which is opposed 
by a corresponding protuberance from the thorax. 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 




The family of Paipicornes have the antennae 
long, club-shaped, and leaf-like. Their feet are 
suited for swimming. The genus Hydrophilus 
is common in Britain, being found in ponds and 
ditches. 

The family Clavicornes have the antennas thick, 
and terminated by a solid mass. In their habits, 
they are partly aquatic and partly terrestrial. The 
Ntcrophorus, or Burying-beetle, is a remarkable 
genus, so called from burying small quadrupeds, 
such as mice and moles. They deposit their eggs 
in the carcass, upon which the young feed during 
their larval stage. 

The Serricornes have the antennas serrated or 
saw-shaped, and the elytra completely covering 
the body. The Wire- 
worm, which devours 
the roots of corn, often 
to a disastrous extent, 
is the larva of Elator 
obsairus. The genus 
Lampyris, or Glow- 
worm, is remarkable for 
the light it emits at 
night The females 
1 ua). especially possess this 

property. The body is 
soft, and the light resides m the last two or three 
sections of the abdomen. The * Death-watch ' 
{Anobium) makes a ticking noise with its jaws 
while perforating wood ; and as this is usual in a 
sick-chamber, and is consequently apt to be heard 
before one dies, the noise so made is held by the 
ignorant mind to be a warning of death, hence its 
common name. 

The Brachelytra are so called from having short 
crustaceous wmg-coverings, and are represented 
by the single genus Staphylinus, which is fre- 
quently seen running about garden walks. 

The Dytisdda are aquatic in their habits. 
Their feet are fringed with broad stiff hairs. They 
have to come to the surface of the water to 
breathe, as their respiratory organs are the same 
as other insects. 

Camivora. — These beetles have been placed by 
entomologists at the head of this order, on account 
of the structure and development of the organs 
which fit them for a mode of life pre-eminently 
carnivorous. The mandibles are armed with 
strong and powerful teeth. They are remarkable 
for the beauty of their colours, and hence the 
name of Tiger-beetles. They prey, even in their 
larval state, upon other insects. The Common 
Beetle {Cicindela campestris) is about half an inch 
in length, of a green colour, with whitish spots on 
the el\-tra, and may be seen running about in 
sandy fields, exposed to the hottest sunshine. 



V. SUB-KINGDOM MOLLUSCA. 

The Mollusca (Lat mollis^ soft) are soft-bodied 
animals, exhibiting bilateral symmetry, usually 
protected by an outer skeleton. The alimentary 
canal is completely shut off from the general 
body-cavity. A nervous system is always present, 
and consists of a single ganglion, or of scattered 
pairs of ganglia. 

The Mollusca may be divided into two chief 
divisions : 

I. Molluscoida^ in which the nervous system 

150 



consists of a single ganglion, or of a principal 
pair with accessory ganglia. Heart very imperfect, 
consisting of a simple open tube, or entirely absent 
II. Mollusca (Proper), in which the nervous 
system consists of three principal pairs of ganglia. 
Heart always well developed, and consisting of at 
least two chambers. 

I. The Molluscoida include the following three 
classes : 



CLASS I.— POLYZOA. 



always 




Bowerbankia i 



The Polyzoa or Bryozoa. — 'Animals 
forming composite colonies, each 
zooid of which consists of an 
alimentary canal suspended in a 
double-walled sac, from which it 
can be partly protruded by a 
process of evagination, and into 
which it may again be retracted 
by invagination. The mouth is 
surrounded by a circle of hollow 
ciliated tentacles.' Pbimatella 
repens, a fresh-water species, may 
be taken as the type. It is a com- 
posite animal ; each individual 
consists of a sac with a double 
wall. "Within this is suspended 
the alimentary canal. The hollow 
ciliated tentacles surrounding the 
mouth are concerned partly in 
respiration, and partly in creating 
currents in the water, and so 
bringing food to the animal. The 
intestine can be protruded from, 
or retracted within the sac by 
means of muscles. The intestine a, oesophagus ; b, giz- 
is curved, so that the anus opens ^^'•■^' ^'o™^*- 

^, ' . XT 1 ^^ »' orifice of mtes- 

near the mouth. No heart or tine, 
blood-vessels are present. The 
fluid within the perivisceral cavity, which is sup- 
posed to represent the blood, is clear and colour- 
less, and is kept in continual motion by the cilia 
lining the inner surface of the body-wall. The 
nervous system consists of a single ganglion, 
placed between the gullet and the anus. They 
{Bryozoa) are all hermaphrodite, and reproduction, 
takes place by budding and by eggs. 

The Sea-mat {Flustra), so common on our 
shores, is a well-known example. It is flat and 
leaf-like in its form, and on the whole it presents 
an appearance like brown sea-weed, for which it 
is often mistaken. But, on examining its surface 
carefully, it is seen to be studded over with little 
openings, through which the little animals can 
protrude their tentacles. 

CLASS IL — TUNICATA OR ASCIDOIDA. 

The Tunicata are defined as having the ' ali- 
mentary canal suspended in a double-walled sac, 
but not capable of protrusion and retraction. 
Mouth opening into the base of a respiratory sac, 
whose walls are more or less completely lined by 
a network of blood-vessels.' 

They are all marine. Take one of the solitary 
forms, Ascidia, as the type. It is globular in 
form, and consists of a double-walled sac, the 
outer layer of which contains cellulose, and is of a 
tough leathery consistence. It is perforated by 
two apertures placed close to each other, one the 
oral, the other the anal opening, so that the whole- 



ZOOLOGY. 




I 



animal resembles a double-necked bottle, hence 
the name of Ascidian (ascus, a bag). The inner 
bag is perforated like the outer. The mouth leads 
into the large respiratory or pharyngeal sac, 
which is continued at its lower end into the 
oesophagus. This res- 
piratory sac is perforated 
by a number of aper- 
tures, and is richly sup- 
plied with blood-vessels, 
for it is here that the 
blood is aerated. The 
intestine is twisted on 
itself, and does not open 
on the surface directly, 
but through the medium 
of a cloacal chamber. 
Section of Social Ascidian : xhe circulatory appara- 
a, mouth; 3, vent; c, stomach; tus differs remarkably 

d, intestinal canal; t, common r^ i-u„4. „r „ii „4.'u„_ 

hlbularstem. ^01" that of all Other 

animals. It consists of 
a simple open tube without valves, which pul- 
sates rhythmically. The blood is driven first 
through one end, and then through the other, 
so that the course of the blood is periodically 
reversed. The nervous system consists of a single 
ganglion placed on one side of the mouth. The 
Ascidians are all hermaphrodite. Some forms 
are composite, as Botryllus, which is also fixed. 
Others, such as Salpa, are free, and float on the 
surface of the sea, their tunic being so delicate 
and transparent that they would scarcely be ob- 
served if it were not for their iridescent appear- 
ance. The Tunicata have attracted a consider- 
able amount of attention lately, from the fact that, 
while in their embryo state, their nervous system 
presents appearances somewhat resembling those 
found in die Kttle fish the Lancelet or Amphi- 
oxus, the lowest of vertebrated animals. 

CLASS III. — BRACHIOPODA. 
The Brachiopoda (arm-footed), are so called 
because of their possessing two long ciliated arms, 
supposed to be for creating currents, thus bringing 
food to the mouth, which is placed at the bases 
of the arms. The animal is inclosed in a bivalve 
shell, lined by a mantle. The two valves of the 
shell are united by a hinge, and kept in position 
by means of muscles. The valves are generally of 
unequal size, the larger one being in some cases 
provided with a beak, which is perforated by an 
aperture, and hence the common name of Lamp- 
shells, from their supposed resemblance to the 
old Roman lamps. The valves with respect to 




Terebratula : 
a, valve with the spiral arms ; h, valve with arms removed. 

the body are placed ventrally and dorsally. The 
Brachiopoda are all marine, and all the known 



living forms are fixed. The shell is lined by, and 
is a secretion from the mantle, a strong muscular 
tunic which invests the soft parts of the animal 
The long arms are in some genera supported by 
a calcareous framework called a carriage-spring 
apparatus. The arms probably perform the func- 
tion of respiration, and the nervous system con- 
sists of a single ganglion, placed between the 
mouth and the anus. It includes the genera 
Lingula, Terebratula, Crania, &c. The Brachio- 
poda were very abundant in some rocks, particu- 
larly in the Silurian formations, where they appear 
to have attained their maximum of development. 
The genus Lingula is found in the lowest fossil- 
iferous rocks, and what is very remarkable, this 
genus still exists at the present day. 

II. The Mollusca proper, which include the 
following four classes : 

CLASS IV.— LAMELLIBRANCHIATA- 

The Lamellibranchiata (plate-shaped gills) — 
including the so-called ' Shell-fish,' as Oysters, 
Mussels, Cockles, &c. They have no head, are 
inclosed in a bivalve shell, and have two lamelliform 
or plate-like gills on each side of the body, and 
neatly arranged within the margin of the shell. 
The body is inclosed in a mantle, from which the 
shell is secreted. The mantle is more or less com- 
pletely attached to the shell. This is indicated in the 




Interior of Mussel : 

A, right valve ; B, left valve ; c, hin^e ; d, stomach ; *, tentacula; 
f, foot ; g, byssus ; h, branchial orifice ; i, vent ; k, termination 
of intestine ; /, liver ; m, gills ; », adductor muscle ; o, ovarium. 

interior of the shell by a line called \}a& pallial line. 
In some bivalves, the edges of the mantle are united, 
so that a closed respiratory chamber is the result, 
to which water is admitted by means of a * siphon,' 
which is just the mantle lobes united and perfor- 
ated by two tubes, through one of which the water 
enters, and is expelled through the other. This 
siphon can in most cases be retracted within the 
shell. In the shell of those bivalves which do not 
possess a siphon, the pallial line is simple, and 
is not indented ; but in those which have a siphon, 
the pallial line forms a deflection inwards, like a 
little bay, to which the muscles that retract the 
siphon are attached. The valves of the shell, un- 
like those in the Brachiopoda, are equal and alike, 
and, with respect to the body of the animal, are 
placed laterally, that is, right and left. Further, the 
valves are closed by muscles called adductors, but 
are opened by an elastic ligament, and a cushion 
of cartilage, which is placed betAveen the beaks of 
the valves, so that, when the creature approxi- 
mates the valves, the elastic ligaments, bemg 
placed behind the beaks of the valves, are put on 
the strain, while the cartilage is compressed, so 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



that, when the animal wants to separate the 
valves, it has only to relax the muscles, and the 
shells fly apart, in virtue of the elasticity of the 
elastic ligaments and the cartilage. In the Brachi- 
opoda, the valves are both dosed and opened 
by means of muscular action. The heart is always 
well developed, and consists of at least two cham- 
bers, and the blood is aerated in the plate-like 
ciliated gills. The nervous system consists of 
three well-defined ganglia. In many of the Lam- 
fllibranchiatd, there is present a muscular organ 
called the foot, which is used in progression. 
This class comprises two sections, namely : 

Section (A). Asiphonida — in which no respir- 
ator)' siphon is present, the pallial line is not 
indentecf, and the lobes of the mantle are free, 
and not united. This section includes the Oyster 
family {Ostreadce), represented by the Ostrea 
edulisy the Common Edible Oyster, which is 
deficient in a foot, and is fixed to the sea-bottom 
by the shell alone. It has its headquarters in 
Britain, and is considered full-grown for the mar- 
ket in from four to seven years. The Common 
Pecten, the type of another family, is so called 
from the resemblance of its shell to a comb, has 
a well-developed foot, and a number of brightly 
coloured spots placed along the edge of the 
mantle, which are supposed to represent eyes. 

The Mytilidcp, represented by the Common 
Mussel {Mytilns edulis), so abundant on our 
shores, has a quantity of hair-like filaments 
(byssus) developed in connection with the foot, 
by which it attaches itself to solid objects. Of 
the family Unionidce, the Unio, or Fresh-water 
Mussel, is noted for producing small pearls. They 
all inhabit fresh water, and the shell is covered 
by a very thick epidermis. The Unio pictorum 
is so called from its shell having been used by 
painters to hold colours. 

Section (B). The Sipho?iida — possess a siphon, 
and the mantle lobes are more or less united. In 
some, the siphons are short, and the pallial line 
simple, as in the Cockle family {Cardiada), in 
which the foot is well developed, and fitted for 
burrowing in the sand of the sea-shore. The 
Common Cockle {Cardtni edtile), which is eaten 
in some localities, can spring to a considerable 
height by means of its bent foot. In others, the 
siphons are long, and the pallial line is indented, 
as in the Myas, which burrow and form a habitat 
for themselves. The Solen, or Razor-shell, sinks 
in the sand with great rapidity. The Pholas has 
a shell composed of arragonite, and can perforate 
timber and solid rocks, thus producing great 
destruction by attacking ships and wooden piles 
in water. Another celebrated species is the 
Teredo navalis, or ship-worm, a worm-like 
animal, furnished with two small shells at its 
anterior extremity, often attaining the length of 
one or two feet, and doing immense damage by 
boring into timber, 

CLASS V. — GASTEROPODA. 

Animals with the head well developed, and 
never inclosed in a bivalve shell. Locomotion 
effected by a horizontally flattened ventral disc 
('foot'), or by a vertically flattened ventral fin- 
like organ. This class includes the univalved 
shells, such as the Snail and Whelk. In the 
mouth, there is a peculiar strap-shaped mastica- 

152 



tory apparatus called an odontophore. The mantle 
is continuous round the body. The heart consists 
of an auricle and a ventricle. In one group, 
respiration is effected by an apparatus for breath- 
ing the air in water {Branchiferd) ; in the other, 
the respiration is aerial {Pulmoniferd). The 
sexes are mostly distinct. The young always 
possess an embryonic shell. The shell is com- 
posed either of a single piece {univalve), or of 
many pieces {multivalve). This class comprises : 

Section (A). Branchifera — in which the respira- 
tion is aquatic. This section includes three 
orders, characterised according to the position of 
the branchiae. 

Order i. The Prosobranchiata have the mantle 
so arranged as to form a vaulted chamber over the 
back of the head, in which the respiratory organs, 
or branchiae, are usually lodged. These gills are 
situated in front of {proson) the heart. This order 
is divided into two sections : 

I. The Siphonostomaia, in which the aperture 
of the shell is notched or produced into a canal. 
They are all marine, and carnivorous in their 
habits — for example, the Whelk family {Buccinidce), 
represented by the Common Whelk {Buccinum un- 
datum), in which the shell is of a spiral form. The 
VolutidcB contain many beautifully marked shells, 
and are chiefly confined to warm latitudes. The 
Cowry family {Cyprceidce), so remarkable for their 
beauty, are largely used as mantel-piece orna- 
ments. In certain parts of Africa, the shell of 
Cyprcea moneta, or Money Cowry, is used by the 
natives as money. The Muricidce {murex, purple) 




Murex tenuispina. 

have a univalve spiral shell, with a small oval 
aperture ending in a straight ascending canal. 
The Strombidce, or Wing-shells, have the aperture 
of the shell much dilated, and the lips expanding 
and extended into a groove leaning to the left. 

2. The Holostomata have the aperture of the 
shell entire. They are chiefly plant-eaters, and 
are either marine or inhabitants of fresh water. 
It includes a great many families — for example, 
the Pate Hides, or Limpet family. In the Common 
Limpet {Patella vulgaris), locomotion is at a low 
ebb, for they seldom move far from the place 
where they are produced. The Haliotidce (Ear- 
shells) are used in making those mother-of-pearl 
ornaments which constitute so much of the beauty 
of works in papier-machd. The Marine Snail 
family {Ttirbinidce) have the shell of a regular 
turbinated form. They are found in great abund- 
ance in the Indian seas, and are used as food, 
many being of large size. The Common Peri- 
winkle {Littorina litter ea) is nearly allied to this 
family. In the Dentalidce, the shell is tubular, 
slightly curved, open at both ends, and shaped 
like an elephant's tusk, hence their name of 
Tooth-shells. The Chiton family {Chit07iidce) have 
multivalve shells, the mantle being covered by 



ZOOLOGY. 



eight testaceous symmetrical plates placed trans- 
versely. These animals live on rocks and stones 




Haliotis tuberculata. 

on the sea-coast, and are distributed nearly over 
the whole globe. 

Order 2. In the Ophisthobranchiata (Gr. 
ophisthen, behind, and bragchi, a gill), the shell 
is rudimentary, and the branchiae are more or 
less completely exposed on the back and sides 
towards the posterior extremity of the body. They 
are commonly called ' Sea-slugs,' and are divided 
into two sections : 

Section (a). Tectibranchiata comprehends those 
species in which the gills are protected by the 
shell or mantle. They are all marine, living 
chiefly on the shore or on floating sea- weed. In 
the family of the BullidcB (Bubble-shells), the shell 
is large and convolute, and in some cases is large 
enough to receive the greater part of the animal. 
The AplysiadcB are slug-like in form, and have 
the mantle very large, and reflected upwards, so 
as to cover in the gills. They possess a merely 
rudimentary shell, and owing to their tentacles 
being turned backwards, like ears, they are popu- 
larly known as * Sea-hares.' 

Section {b). Nudibranchiata, in which the 
shell is absent, and the 
branchiae are exposed on 
some part of the back 
in the form of a rosette. 
It includes all the naked 
marine Gasteropods, as 
Doris (Sea-lemon), Tri- 
ton, and Tethys. They 
are elegant and beautiful little creatures, like 
slugs, and are generally ornamented with beautiful 
colours. They are found creeping on sea-weeds 
or attached to stones at low-water. 

Order 3. The Heteropoda have the foot com- 
pressed into a thin vertically flattened ventral 
fin, by means of which locomotion is effected. 
They are free-swimming and pelagic. This order 
comprises two families, Firolid(B and Atlantidce. 
In the FirolidcB, the shell is absent, or exists in a 
rudimentary form, and protects the circulatory 
and respiratory organs, including the genera Cari- 
naria and Firola. In the Atlantidce, such as 
Atlanta and Bellerophon, the shell is large, and 
■capable of containing the whole animaL 

Section (B). The Pulmonifera are characterised 
by having their respiratory organs so arranged as 
to breathe air directly. The mantle is inflected 
so as to form a pulmonary chamber, into which 
air is admitted from without, and where it comes 
in contact with the plenus of vessels with which 
the wall of the chamber is supplied. They are 
hermaphrodite. Most of them are land animals : 




Doris : a, gills. 



although a few are aquatic, living chiefly in fresh 
waters and brackish pools, they are forced to 
come to the surface to breathe. This section 
includes two orders. 

Order 4. Inoperculata. — The animals in this 
order are not provided with an operculum for 
closing the shell. The family of the Helicida 
(Land-snails) are among the most familiarly 
known of all animals. The shell is large, and 
capable of containing the entire animal. They 
feed exclusively on vegetables, and the destruc- 
tiveness of the Garden-snail {Helix hortensis) is 
well known. In tropical climates, the genus 
Bulimus sometimes attains to a great size. The 
tropical Achatina is distinguished by the beauti- 
ful colours of its shell. The family of the 
LimacidcB (Slugs) are naked snails, and are 
very destructive to vegetables. The head bears 




Mature SnaiL 

four tentacula, and at the end of the longer pair 
the eyes are situated. These tentacula (usually 
called the ' horns ') can be drawn in by a process 
resembling the inversion of the finger of a glove. 
The family of the Lym7i(eidce (Pool-snails) reside 
in stagnant waters, feeding upon plants and seeds. 
The shell is thin, well developed, with the aper- 
ture simple, and the lip sharp. The Lymncea 
is connected with the development of the immature 
cercaria into distoma. In the genus Planorbis 
(Marsh-snails), the coils of the shell are all upon 
the same plane. 

Order 5. — In the Operculata, the shell is pro- 
vided with an operculum, which is a horny or 
calcareous disc attached to the foot, and is drawn 
into the mouth of the shell by the contraction of 
the animaL It includes the genus Cyclostotna, a 
snail-like animal provided with a thin spiral shell, 
with the margins usually reflexed all round. 

CLASS VI. — PTEROPODA. 

The Pteropoda (wing-footed) are free-swimming 
oceanic forms, provided 
with two wing-like ap- 
pendages on each side 
of the anterior extrem- 
ity of the body. They 
are small animals, and 
exist in all seas, but are 
found in enormous multi- 
tudes in the Arctic and 
Antarctic Oceans. One of 
them, the Clio Borealis, 
forms the chief food of 
the whale, which swallows Example of the Pteropoda 
thousands at a mouthful. (Cleodora pyramidata). 
They are eminently car- 
nivorous, feeding upon minute crustaceans and 
other sinall animals. 




CHAMBERS'S INFORMATION FOR THE PEOPLE. 



CLASS VII.— CEPHALOPODA. 

The Cephalopoda are so named from having 
their limbs arranged in immediate connection 
with their head. These limbs are eight or 
ten in number, and perform all the functions of 
feet, arms, and feelers. The body is inclosed 
within a muscular mantle-sac. Through the ante- 
rior tubular orifice (' funnel 0, the effete matter of 
respiration is expelled. They are the most highly 
organised of invertebrate animals, presenting rudi- 
ments of an internal skeleton. The eyes are well 
developed, and, in most of the existing species, 
organs of hearing are present. The head is large 
and conspicuous. They possess distinct hearts 
for the systemic and pulmonary circulations, and 
highly complicated nervous, digestive, secretory, 
and respiratory organs, which are in the form of 
tvvo or four plume-like gills, situated within the 
mantle. They are all marine and carnivorous. 
Order i. — The Dibranchiata are specially 
suited for swimming rapidly 
through the water. These 
animals have two gills and 
three distinct hearts ; an ink- 
sac for secreting and emitting 
an inky fluid ; and the arms 
never above ten in number, 
and supporting suckers. The 
funnel is a complete tube, and 
the shell is internal, or, if 
external, it is not chambered. 
The Cuttle-fish are the most 
typical members of this order. 
They swim backwards by 
means of the jet of water 
expelled through the funnel, 
and by means of their arms 
and suckers they creep on the 
bottom of the sea, and retain 
a forcible hold of their prey. This order is divided 
into two sections, characterised by the number 
of their arms. 
Section i. Octopodidaa are distinguished by the 




Cattle-fish. 




Aigonaat 

possession of feight arms. They are very voracious 
animals, and to this family belongs the Poulpe 



{Octopus) of the Mediterranean, whose shell is 
placed internally. It is eaten as a regular article 
of diet in the south of Europe. In the Paper 
Nautilus {Argonauta), the female alone is pro- 
tected by a very delicate and beautiful external 
non-chambered shell. The male argonaut is only 
about one inch in length. 

Section 2. The Decapoda have ten arms, two of 
which are longer than the others (tentacles), of 
a rounded form, and club-shaped at the extremity. 
The suckers are placed on stalks, and the body has 
a fin-like organ on each side ; further, the shell is 
always internal. It includes the Calamaria, or 
Squids — for example, Loligo, the shell of which is 
homy, and is called the 'cuttle-fish pen.' The 
common British species (Z. vulgaris) is used as 
bait by the fishermen, and is often cast upon the 
shores in great quantity after high winds. In 
Sepia, the shell is calcareous, and is called ' cuttle- 
bone,' and was formerly used in medicine. This 
section also includes the extinct Belemnites, or 
Jove's Thunderbolt 

Order 2. The Tetrabranchiata — have four 
gills, and are protected by an external chambered 
shell with simple partitions or septa, perforated 
by a tube or siphuncle. The last chamber of the 
shell is the largest, and contains the body of the 
animal. There is no ink-sac. The arms are 
numerous, and devoid of suckers. It consists of 
only one living family, the NautilidcE, of which 
the Pearly Nautilus {Nautilus pompilius), which 
inhabits the tropical seas, is the type. The shell 
of N. pompilitis is partitioned off by septa into 
chambers which gradually in- 
crease in size towards the 
mouth of the shell, where the 
largest chamber is left for the 
habitation of the animal, while 
the other chambers are filled 
with air. The septa are per- 
forated in the centre by aper- 
tures, through which there 
passes a vincula siphuncle, 
communicating with the cham- 
ber where the heart is placed. 
This order was abundantly re- 
presented in past time by such 
genera as Ammonites, Orthoceras, and CeratiteSy 
which are now entirely extinct. 

In the Dibranchiata, the mode of reproduction 
is peculiar. The sexes are distinct. One of the 
arms of the male enlarges, becomes cystic, and 
spermatozoa are developed in its interior. Thus 
changed, it is said to be hectocotylised. It is 
then detached, and swims about, ultimately burst- 
ing, and depositing the spermatic fluid within the. 
pallial chamber of the female. 




Ceratites nodosus. 



VI. SUB-KINGDOM VERTEBRATA. 

The last and highest division of the Animal' 
Kingdom is composed of animals which have 
their segments arranged along a longitudinal axis, 
and exhibit bilateral symmetry. The fundamental 
character of vertebrates is the possession of an 
internal central axial structure called the spine or 
vertebral column; hence the name of the sub- 
kingdom. This structure may be bony or carti- 
laginous, or both, and it shuts off the nervous 



ZOOLOGY. 



system from the general body cavity. In a typi- 
cal vertebrate, such as man, it consists of a senes 
of bones or vertebrcB, which are articulated to- 
gether in such a manner as to permit of a greater 
or less degree of flexibility, and giving attach- 
ment to appendages, of which some support and 
protect important viscera, while others assist in 
the motion of the animal. Each vertebra has 
more or less the form of a ring, and when the 
various vertebrae are articulated together, the 
whole is termed the vertebral column, or back- 
bone. The ring-like apertures in each vertebrse, 
when thus joined together, form a tube, in which 
the spinal cord is lodged, and from which the 
nerves which supply the body are given off. The 
vertebral column is placed dorsally, and serves 
not only as a surface of attachment for muscles, 
and a central axis, but also as a protection for 
the main masses of the nervous system, which 
are thus also placed dorsally, and are separated 
by a partition from the general body cavity. The 
anterior extremity of the spinal column is expanded 
in a box or case, the skull (technically called the 
cranium), in which the bratn is lodged. The 
brain is continuous with the spinal cord through 
an opening in the base of the skull, called the 
forajneti viagnum. The theory that the skull is 
composed of a series of vertebras, whose arches 
are expanded, and unite to inclose and protect the 
brain, originated with Goethe, in 1791, on his 
picking up an old and broken sheep's skull amidst 
the sandy dunes of the Jewish cemetery in Venice. 
Lorenz Oken came independently to the same 
conclusion, and in 1807 published his vertebral 
theory of the skull. According to Professor Owen, 
the skull is a continuation of the back-bone, and 
consists of four vertebrae or segments, correspond- 
ing to the four consecutive enlargements of the 
nervous system which we call the brain. These 
segments, reckoning them from behind forwards, 
are termed the occipital, the parietal, the frontal, 
and the nasal segment. In the embryo of all 
vertebrates, a structure called the tiotochord {notes, 
back, and chorde, string), or chorda dorsalis, is 
invariably present. It generally disappears in the 
adult, but it is persistent in some fishes. It is a 
cellular, rod-like structure, situated immediately 
tinder the spinal cord, and out of which the 
vertebral column and some other structures are 
developed. The general bony fabric of which the 
vertebral column is the main or central part, is 
internal, an arrangement contrary to that in the 
lower provinces of creation, where the hard and 
sustaining parts are external. The limbs never 
exceed four in number, and are turned ventrally, 
serving for progression, and occasionally for pre- 
hension or seizing, but subject to many variations, 
according to the element in which the animal 
lives, and the nature of its necessities. By reason 
of their superior nervous system, vertebrated 
animals stand decidedly above other provinces 
in intelligence. With the single exception of the 
Lancelet, all the vertebrata have red blood, which 
is due to presence in the blood of an innumerable 
multitude of minute red, round or oval bodies, 
called blood-corpuscles, about -s-sVir of an inch in 
diameter, the fluid in which they float being itself 
colourless. 

This sub-kingdom is divided into the five great 
classes — Fishes {Pisces), Amphibians {Amphibia), 
Reptiles {Reptilia), Birds {Aves), and Mammals 



{Mammalia). By Professor Huxley, the fishes 
and amphibia are grouped together under one 
section, and called" Ichthyopsida, because at some 
period or other they breathe by gills. The reptiles 
and birds he puts into another section, under the 
name Sauropsida, characterised by their never 
possessing gills, by the skull being articulated to- 
the vertebral column by a single occipital con- 
dyle, by the articulation of the lower jaw to the 
skull through the intervention of a distinct bone 
(the OS quadratum), and by the ramus of the 
lower jaw being composed of several pieces. He 
retains the name Mammalia for the mammals^ 
for the characters of which see Mammalia. 

CLASS I. — FISHES. 

In this class, the animals are wholly aquatic, 
and breathe by means of gills or branchice. The 
heart consists of a single auricle and ventricle. 
The auricle receives the blood from the system, 
and propels it into the ventricle, by which it is 
sent on to the gills, where it is aerated by being 
exposed to the air contained in the water, and is 
then distributed throughout the body. The blood 
is cold — that is, it never rises in temperature above 




Fish: 

a, dorsal fins ; b, pectoral fin of one side ; c, ventral fins ; d, ana)-- 

fin ; e, caudal fin, or tail ; f, operculum. 

the temperature of the surrounding medium. The- 
four limbs of a typical vertebrate assume in fishes 
the form oi fins, and are generally, although not 
always, all present, the first pair being the pectoral, 
the second pair the ventral fins. When the 
ventrals are placed far forwards, underneath or 
in front of the pectorals, they are called jugular 
fins. There are other fins, however, which are 
not placed in pairs, towards the sides, but verti- 
cally in the middle line ; one or more {dorsal) oa 
the back; one or more {anal) on the ventral 
aspect, behind the anus ; and one {caudal) at 
the extremity of the tail. These last are called 
the unpaired fins, in contradistinction to the 
former or paired fins. The chief propelling power 
resides in the vertically flattened caudal fin or 
tail, which is used by the fish in the same way as 
a single oar is employed in sculling along a boat 
The pectoral and ventral fins serve chiefly for 
balancing the body, while the dorsals and anals, 
like the keel of a ship, keep it in its proper position. 
The surface of the body is usually covered with 
scales. In many species, the gills are covered by 
a corneous plate, styled the operculum. In those 
fishes which have a well-formed vertebral column, 
the individual vertebrae are hollowed on each side, 
with a bag of lubricating fluid between them, an 
arrangement which gives great suppleness and 
agility of movement They are nearly all ovipar- 
ous, and some are amazingly productive. The- 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



female deposits her eggs or spawn, leaving to the 
male the duty of afterwards fertilising them. The 
teeth of fishes are chiefly designed to serve as 
means of seizing prey. They are not only placed 
on the jaws, but also on the tongue, palate, and 
4)ther parts of the passage leading to the stomach. 
The lungs of other vertebrates are represented in 
fishes by the swimming-bladder, which is of 
ser\'ice in floating the animal. 

Order i. The Pharyngobranchii — includes only 
a single genus, the Amphioxus lanceolatus, or 
Lancelet, which differs remarkably from other 
fishes. It has neither skull nor brain ; the lower 
jaw and limbs are absent. The spinal column 
exists in its embrj-onal form. The heart is repre- 
sented by pulsatile swellings upon the great 
vessels. The mouth is in the form of a longi- 
tudinal fissure, surrounded by filaments, and leads 
into a pharynx perforated by clefts, which are 
filiated, and perform the function of respiration. 
This singular little fish, which measures about one 




Lancelet {Amphioxus lanceolatus) : 

«, mouth, seen from below ; b, general figure ; c, hyoid bone, with 
filaments attached. 

inch in length, is found burrowing in the sand on 
the shores of the Mediterranean. The body is 
lanceolate ; and running along the dorsal surface 
in the median line is an imperfect crust or fin, 
which expands at the tail into a lancet-shaped 
caudal fin. 

Order 2. The Marsipobranchii-Avaso. the body 
cylindrical in form, and destitute of limbs. The 
skull and spinal column are cartilaginous, and 
the lower jaw is absent. The mouth is round, and 
supported by a cartilaginous ring, and adapted 
for adhering to prey. The skin is soft, with 
scarcely a vestige of scales. The gills are sac- 
like, communicating internally with the pharynx, 
and externally by one or more openings situated 
on the side of the body near the head. It com- 
prises the Lampreys (Petromyzon), characterised 
"by having roundish gill orifices on each side of 
the neck, and by the possession of a tooth within 
the cartilaginous ring, with which they tear their 




rivers. The Myxitie (Hag-fish) is blind, and is 
found parasitic in the interior of other fish, usually 
the cod, into which it penetrates by means of its 
singular curved tooth. In this genus, the nasal 
sac opens posteriorly into the pharynx. 

Order 3. The Teleostei, or ' osseous ' fishes 
have a well-ossified skeleton, and the skull is 
composed of numerous bones. A lower jaw is 
present The gills, which are supported upon 
bony arches, are tufted and comb-like in shape, 
and lodged in two branchial chambers, each of 
which communicates internally with the pharynx, 
and from which the water passes away by a single 
aperture (gill-slit), which is covered with a bony 
operculum. The bulbtts arteriosus, which is 
situated immediately in front of the ventricle, is 
not contractile, and there is never more than a 
single row of valves separating it from the 
ventricle. The fins, when present, are supported 
by rays. The nasal sacs do not communicate 
posteriorly with the pharynx. 

Sub-order (A). The Malacopteri — have soft or 
many jointed fins — that is, fins which are sup- 
ported by bones, which split up longpitudinally as 
they diverge from a common point of insertion. 
Further, these bones are divided transversely into 
shorter pieces. A swimming-bladder is always 
present, and communicates with the gullet. This 
sub-order is divided into two groups : i. Apoda, 
from which the ventral fins are absent, compris- 
ing the well-known Murcenidce, or Eel tribe. They 
are all lengthened in form, have the spine very 
flexible, the skin soft and thick, and the scales 
almost invisible. Many of them inhabit rivers, 
while others are marine, as the Conger, which is 
from four to six feet long, and destitute of both 
pectoral and ventral fins. The Common Eel 
{Anguilla) can live for some time out of the 
water. This is due to the smallness of the gill 
apertures, which keep the breathing organ moist 




Commoii Lamprey {Petromyzon marinus). 

prey. There' is a marine species two or three 
feet long, and other smaller ones which inhabit 

156 



Electrical Eel {Gymnotus electricus). 

The most remarkable form is the Gymnotus, or 
Electrical Eel. It is a native of the South Ameri- 
can rivers. It attains the length of five feet, 
and can communicate a shock powerful enough 
to stun men and horses. The electrical apparatus 
is largely supplied with nerves, and extends 
throughout the greater part of its body. By 
giving these shocks, the animal is greatly ex- 
hausted, and requires rest and nourishment 
before it can renew them. In this genus, the 
anus is placed in front of the gill openings. The 
second group — namely, the Abdominalia — have 



ZOOLOGY. 



the ventral fins attached to the abdomen behind 
the pectorals. It includes the greater number of 
the fresh-water fishes. There are five families. 

The CyprinidcB (Carp tribe) are all fresh-water 
fishes. The mouth is shallow, the jaws feeble, 
and the pharynx strongly toothed. They feed 
chiefly on seeds and decomposing vegetable 
matter. One of the finest European species is 
the Carp {Cyprinus carpid), which is imported 
into England, and thrives well in ponds and lakes. 
The Barbel and the Cobitis or Loche are allied 
species well known to anglers. The Gold-fish 
of China (C auratus), now naturalised in this 
country, also belong to this family. The Anableps, 
from the rivers of Guiana, has the cornea and iris 
divided by transverse bands, so as to give the fish 
the appearance of having four eyes. 

The EsoeidcB (Pike tribe), the most voracious of 
the fresh-water fishes, are characterised by the 
absence of fatty matter in the dorsal fin, and by 
the position of this opposite to the anal. fin. The 
Pike {Esox Indus) sometimes weighs forty pounds, 
and is very destructive to the smaller fishes in the 
ponds and rivers which it inhabits. The Gar- 
fish, or Sea-pike, which frequents the British 




Pike, or Jack (Esox lucius). 

shores, sometimes attains the length of eight feet. 
The Mackerel-pike, or Saury, a British species, 
is gregarious in its habits, and is preyed upon by 
porpoises and tunnies. 

The SiluridcB (Sheat-fishes) have no true scales, 
the skin being either naked or covered with bony 
plates. They inhabit the rivers of warm climates. 
The genus Silurus have a strong spine in front of 
the dorsal fin, which can be laid flat or raised 
perpendicularly, so as to form a formidable 
weapon. The Malapterurus electricus of the 
Nile and rivers of Central Africa, which attains 
the length of twelve inches, has electric properties 
similar to those of the torpedo and gymnotus. 

The SalmonidcE (Salmons and Trouts) are very 
extensively, indeed almost universally, diffused over 
the globe ; some of them being confined to fresh 
water, and others passing a part of their lives in 
the sea, but resorting to rivers to deposit their 
eggs. They are distinguished by the fatty deposi- 
tion in the dorsal fin. All of this family are 
clouded with dusky patches when young, and 
many remain permanently spotted. The flesh of 
most of them is esteemed as food. The Salmon 
inhabits the seas of comparatively cold regions, 
ascending the rivers for the purpose of spawning, 
at seasons varying with the climate. They swim 
against powerful streams, and leap up cascades of 
considerable elevation, and find their way to the 
brooks and small lakes of lofty mountains. After 



this operation is accomplished, they return to the 
sea, followed by the young fish. The best known 
British species are the Common Salmon {S. salar)^ 




Salmon [Salmo salar). 

the Salmon Trout {S. trutta), and the Gray or 
Bull Trout {S. eriox). The Trout appears to vary- 
much in size and colour according to the climate 
and other conditions of its residence, so that it is 
difficult to distinguish species from mere varieties. 
The Common Trout {Salmo /ario), whose growth 
is wonderfully rapid, is too well known to require 
description. The Smelt {Osmerus) and Grayling 
{Thymallus) of British rivers, and the Capelin, 
which is used on the shores of Newfoundland 
for bait, also belong to this family. 

The ClupeidcB (Herring tribe) is one of the most 
important families in the whole class, for the 
amount of food it supplies to man. The fishes 
belonging to it resemble the Salmonidae in many 
characters, but differ in having no fatty matter in 
the dorsal fin. They chiefly inhabit the seas of the 
temperate zone. The Herring {Clupea harengus) 
usually lives in open ocean, but periodically visits 
the nearest coast in immense shoals to deposit its 
spavm. There are many species, differing but little 
from the herring. Thus, the Pilchard is caught on 
the Cornwall coast, the Sardine on the west coast 
of France and in the Mediterranean, where the 
Anchovy, well known for its rich and peculiar 
flavour, also abounds. The Sprat, Whitebait, and 
Shad belong to the same family. 

Sub-order (B). The Atiacanthini — have the fins 
entirely 'soft.' The ventral fins, if present, are 
brought forward beneath, or even in advance of 
the pectorals. If the swim-bladder is present, it 
never communicates with the gullet by a duct. 
Two groups are included under this sub-order : 

1st Group, the Apoda, which are destitute of 
ventral fins. The Sand-eels {Ammodytes) belong 
to this group. They bury themselves in the sand 
during the ebb of the tide, and are used as bait by 
the fishermen. 

In the 2d Group, the Sub-branchiata, the ventral 
fins are present It comprises two families — 

Family GadidcB (the Cod tribe) are easily known 
by the softness of all their fins, and by having the 
ventrals inserted under the throat, and pointed. 
To this family belong the Haddock, Whiting, 
Ling, Pollack, and the Cod itself Besides being 
used as food, the oil obtained from their livers i& 
very serviceable in the arts and in medicine. 

The second family is that of Pleuronectidcz^ 
(the Flat-fish or Flounder tribe). The body 
is compressed from side to side, and margined 
almost throughout by long dorsal and anal fins. 
The two flat surfaces — one of which, in the ordin- 
ary position of the fish during life, is above, and 
the other below — are in reality the two sides of 
the fish, differing in several important respects. 
The bones of the head are singularly twisted, so 
that both the eyes are placed on one side of the 

167 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



laody, and this, which is always the upper, is dark 
in its colour, whilst the opposite side is always 
white. The two sides of the mouth are not equal, 
and the pectoral fins rarely so. On the other 
hand, the dorsal fin, which runs along one of the 
lateral edges, corresponds with the anal, which 
occupies the other, and with which the ventrals 
are sometimes united. They frequent the bottom 
of the sea, and swim along by an undulating 
motion of the whole body, while the colour of their 
upper surface usually corresponds closely with 
that of the ground on which they he, and thus 
they escape the observation of their enemies, 
and are unnoticed by the small fishes on which 
they prey. The Flounder, Turbot, Brill, Plaice, 
Halibut, and Sole are the chief species on our 




Sole (Solta vulgaris), 

own coasts ; they are agreeable and wholesome 
as food. 

Sub-order (C). The Acanthopteri (Spiny-finned 
Fishes)— in which one or more of the first rays in 
the fins are supported by a 'spiny,' or injointed 
bony ray. There is no duct to the swim-bladder. 
The ventral fins are situated on the breast or 
throat in the neighbourhood of the pectorals. 
The scales are generally ctenoid or comb-like. 
This sub-order includes a g^'eat number of families : 

The LabridiB (Wrasse or Rock-fish tribe) are 
known by the thickness and fleshiness of their 
lips, whence their name. Those of the genus 
Labrus are called ' old wives ;' and this family con- 
tains a large number of species, which are prin- 
cipally inhabitants of tropical seas, and they are 
of but slight direct importance to man. Some of 
the tropical forms are remarkable for the beauty 
of their colours. 

The Fistularida (Pipe-mouthed Fishes) are 
recognised by their very prolonged muzzle. They 
are chiefly found in warm latitudes, but Sea-snipe 
{Centriscus scolopax) is occasionally found on the 
Cornish coast as a straggler from the Mediter- 
ranean. 

The Percida (Perch tribe) are numerous in the 
waters of warm climates, some species inhabiting 
the rivers, and others the sea. Their bodies are 
oblong, and covered with hard scales ; and the 
gill-covers are toothed at the margin. The teeth 
are minute and set together in numerous rows. 
The ventral fins are generally placed under the 
pectorals. This family includes the Common 
Perch {Perca fluviatilis), which is found in almost 
€very piece of clear fresh water, and a large 
number of marine fishes used as food on different 
shores. Some of the most remarkable are the 
Trachinus, or Weaver, which has a very pro- 
longed and sharp dorsal spine, capable of inflicting 
a severe injury ; the PolynemuSy or Mango-fish 
of the Ganges, which has the pectoral fins on each 
side prolonged into threads thrice as long as the 

168 



body; the Uranoscopus (Star-gazer), so called 
from the position of the eyes on the top of the 




Perch {Perca fluviatilis). 

nearly cubical head ; the Mullus surmtilletus 
(Red Mullet) of British seas, and many others. 

The TriglidcB (Gurnard tribe) bear a resem- 
blance to the perches, but have the head armed 
with spines or hard scaly plates. The Gurnards, 




Gurnard {Trigia pini). 

the Sticklebacks, and the Sebastes, or Norway Had- 
dock, the spines of which are used by the Green- 
landers as needles, belong to this family. The most 
interesting of all is the Dactylopterus, or Flying- 
fish. This has a kind of supplementary pectoral 
fin on each side, formed of a membrane stretched 
over finger-like processes, which in the gurnards 
are unconnected. By the impulse of these on the 
surface of the water, the flying-fish can rise several 




Flying-fish {Exocxtus volitans). 

feet into the air, and suspend themselves above 
the surface for a few seconds, often skimming 
lightly over it for a considerable distance. 

In the Sparidce (Sea-bream tribe), the genus 



ZOOLOGY. 



Sparus has the jaws covered with round flat teeth, 
like pavement, for grinding down the stony corals, 
and the hard shells of mollusca on which they 
principally feed. 

The ChcEtodontidcB have the body compressed, 
and the soft and spinous parts of their dorsal fins 
covered with scales, so as not to be distinguished 
from the rest of their body. The Chcetodon ro- 
stratus, a native of India, which has a very pro- 
longed snout, has the faculty of shooting insects 
with drops of water projected from the mouth, 
and it then seizes them as they fall. 

The next family, ScomberidcB (the Mackerel 
tribe), is one of very great importance to man. It 
comprises a large number of genera, a vast collec- 
tion of species, and numberless individuals. The 
aspect of the Common Mackerel, with its spindle- 
shaped, beautifully coloured, smooth, and small- 
scaled body, is well known. It very rapidly dies 
out of water, and soon becomes tainted. The 
Tunny {Thytmus vulgaris), which frequents the 
Mediterranean, is a much larger fish, sometimes 
attaining the length of twenty feet. The Xiphias, 
or Sword-fish, which abounds in the Mediter- 
ranean, and often attains the length of fifteen 
feet, also belongs to the family. It can drive its 
long-pointed beak into the timbers of a ship. The 




Dory (Zeusfaber). 

Dory — remarkable for the filamentous prolonga- 
tions from its dorsal fins — is much prized by 
epicures. And lastly, may be mentioned the Cory- 
phana, commonly known as the Dolphin. This 
is a large and splendidly coloured fish. It has 
long been celebrated for its change of colour when 
dying. It swims with great rapidity, and is very 
voracious, committing great havoc among the 
flying-fish. 

The small family of the Tcenidce (Ribbon-shaped 
Fishes) are remarkable for the lateral flattening of 
their body. The Lepidopus argyreus (the Scab- 
bard-fish) belongs to the family. 

The MugilidcB are lengthened and often nearly 
cylindrical fishes, with a somewhat projecting 
snout, and a very small mouth placed beneath it. 
They are gregarious in their habits, frequenting 
the mouths of rivers in large troops, and con- 
stantly leaping out of the water. There are several 
species found in European seas, but the one best 
known on the British coast is the Mugil chelo, or 
Thick-lipped Gray Mullet. 

The family of the AnabatidcB---oi which the 
Climbing Perch of India {Anabas scandens) is an 
example — are remarkable for having the superior 
pharyngeal bones divided into irregular leaves, 
placed in the base of the skull, and containing 



cells among them, in which a supply of water for 
moistening the gills may be carried, thus enabling 
the animal to continue respiration out of its 
proper element By means of this apparatus, 
these fishes are enabled to quit the pool or rivulet 
which constitutes their usual element, and move 
to a considerable distance overland. They are 
able not only to traverse plain grounds, but can 
even climb trees in search of their prey. 

The members of the family Gobiodee (or Goby 
tribe) are known by the thinness and flexibihty of 
their dorsal spines. Many of them are remark- 
able for producing their young alive. This is the 
case with the Blenny, of which several species 
frequent the British shores, living in small troops 
among the rocks. They are remarkably tenacious 
of life, and are capable of being kept a good many 
days in moist grass or moss, but they are of little 
value as an article of food. One of the most inter- 
esting species of this family is the Anarrhicas 
lupus, or Sea-wolf. It inhabits the northern seas, 
and is often met with on our shores, attaining the 
length of six or seven feet. It is very formidable 
in aspect, is remarkably strong, very active, and 
equally ready to defend itself or attack an enemy. 
In the Echeneis remora, or Sucking-fish, the 
upper surface of the head is furnished with a 
series of thin cartilaginous plates, by means of 
which the animal can attach itself to any kind of 
surface. It seems to prefer bodies in motion, and 
is not unfrequently found adhering to large fish, 
and to the bottoms of vessels, whose course it was 
once absurdly believed capable of arresting. It is 
abundant in the MediteiTanean. The true Gobies 
have the ventral fins placed far forwards and 
united at their bases ; they are chiefly remark- 
able for the nest which they construct among 
the sea-weed for the protection of their young. 

The last family, the Lophiidce, have the wrist 
bones much elongated, upon which the pectoral 
fins are supported, thus forming a kind of arm. 
This conformation gives these fish a very strange 
appearance. One of the most curious is the 
Lophius piscatorius (Angler or Fishing- frog) of the 
British seas. It derives its name in part from its 
wide gaping mouth, which is placed transversely, 
and furnished with many sharp-curved teeth, and 




Angler (Lophius piscatorius), 

in part from the peculiar manner in which it 
angles for its prey. There are some curious 
appendages to its head, which terminate in long, 
round, and rather brilliant filaments. The animal, 
which sometimes measures four feet in length, 
lurks in the mud, and puts these appendages in 
vibration ; they are mistaken for worms by small 
fishes, which they attract, and these are gulped 
down the capacious maw of the lophius. To such 
an extent is this voracity carried, that the angler 

189 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



is often an article of value for the fish which it 
has in its stomach, although its own flesh is but 
little worth. 

Sub-order (D). The Plectogttathi—zc^^roTLch the 
Cartiligines in many points of organisation ; prin- 
cipally, however, in the slow ossification of the 
skeleton, and the imperfect structure of the mouth. 
They derive their name from the union of the 
upper jaw to the skull ; so that its motion is ob- 
tained, not from a distinct joint, but by the mere 
flexibility of the half-ossified cartilages. The gill- 
lid is concealed under the thick skin, with only a 
small opxming ; the ribs are scarcely developed ; 
and there are no true ventral fins. This order 
contains two families : 

The family of the Sclerodermata contain fishes 
which are remarkable for their hard and granu- 
lated skins. They have the head prolonged into 
a muzzle : at the extremity of this is the mouth, 
which is armed with a series of distinct teeth. 
The Ostracion (Trunk-fish), which is found in the 
Indian and American seas, has the whole of the 
body except the tail covered with an inflexible 
suit of bony armour, composed of bony plates. 
The Balistes (File-fishes) have the dermal skeleton 
in the form of small grains, leaving the skin a 
certain amount of flexibility. They are prin- 
cipally inhabitants of warm seas. 

The Gymnodonta (Naked-toothed fishes) are 
distinguished by having the jaws covered with an 
ivory-like substance arranged in small plates, 
which are reproduced as soon as destroyed by use. 
They live on Crustacea and sea-weed. The most 
remarkable species of this family are the Spinous 
Globe-fishes, Diodon and Tetraodon, which have 
the power of blowing themselves up like balloons, 
by filling with air a large sac which nearly sur- 
rounds the abdomen. They are defended by 
spines over their whole surface, which are erected 
as they are inflated. The Sun-fish has a body of 
somewhat similar form, but incapable of inflation ; 
from the shortness of its tail, it looks like the 
anterior half of a fish cut in two in the middle. 
There are only two British species of sun-fish 
(Orthagoriscus), and some specimens have been 
known to weigh 300 pounds. 

Sub-order (E). The Lophobranchii — are a small 




Hippocampus brevirostres. 
group, which have the gillg arranged in tufts in 

160 



pairs upon the branchial arches. The swim- 
bladder is destitute of an air-duct. The body is 
covered, not with small scales, but with shields or 
plates, which often give it an angular form. In 
general, they are of small size, and almost with- 
out flesh. The Syngiiathus (Pipe-fish) possesses 
a long tubular snout It is peculiar for the pro- 
tection it afibrds to its young. The eggs are 
conveyed into a sort of pouch under the body 
of the male, and are hatched there, the young 
fry afterwards finding their way out. Some of 
these are found in the British seas ; as are also the 
Hippocampi, commonly called 'sea-horses,' from 
the resemblance of the upper part of the body to 
the head and neck of a horse in miniature. The 
tail is prehensile, and they climb or hold on to the 
stalks of marine plants by its means. 

Order 4. The Ganoidei — are a group of which 
there are few living representatives at the present 
day, but they attained an enormous development 
during the Palzeozoic period, when they were 
represented by such genera as Pterichthys, Coc- 
costeus, Pteraspis, and Cephalaspis, from the Old 
Red Sandstone. In this group of fishes, the 
endo-skeleton is very imperfectly ossified ; in fact, 
in many of the fossil forms the skeleton was 
entirely cartilaginous. The exo-skeleton consists of 
plates or scales, which are composed of an upper 
layer resembling enamel, and termed ganoine, 
and an under layer of true bone. These plates in 
some genera are of a rhomboidal form, and deli- 
cately sculptured, and being placed edge to edge, 
afibrd an efficient yet flexible investment for the 
soft parts within. The ventral fins are usually 
present, but they are placed far back near the 
anus. In some recent forms, such as the Polyp- 
terus, and in many extinct forms, the paired fins 
have their fin-rays arranged round a central lobe. 
Those fishes with fins so constructed are * fringe- 
finned,' and belong to the division Crossopterygidce 
of Huxley. The tail is generally unequally lobed, 
when it is said to be ' heterocercal.' The gills 
have the same structure as in the Teleostei. The 
swim-bladder possesses an air-duct which com- 
municates with the pharynx. The bulbus arte- 
riosus is rhythmically contractile, and is separ- 
ated from the ventricle by several rows of valves. 
The intestine is furnished with a folding of its 
mucous membrane, so as to form a spiral valve. 

The Lepidosteiis (Bony Pike) of the rivers and 
lakes of North America, and the Polyp terns of the 
Nile, are recent examples. The fonner has the 
jaws prolonged into a long narrow snout, and the 
tail heterocercal ; the body is protected by trans- 
versely arranged rows of ganoid plates. The latter 
has its dorsal fin broken up into a series of small 
fins, each of which has a strong spine in front,, 
and a soft fin attached to it posteriorly. The 
SturionidcB, or Sturgeons, also belong to this- 
order. In them the notochord is persistent, and 
the tail is heterocercal. They are found in the 
Black and Caspian Seas, and ascend the rivers 
for the purpose of spawning. They are extremely 
valuable to man, their roe furnishing the caviare 
so much esteemed in Russia, and the air-bladder 
furnishing isinglass. The Common Sturgeon 
{Accipenser sturio) of the British coasts is about 
six feet long ; but the Beluga (A. huso) of the 
Caspian Sea measures fifteen feet in length. The 
Spatularia (Paddle-fish) of North America is a. 
nearly allied form. • 



ZOOLOGY. 



Orx)ER 5. The Elasmobranchii, including the 
Sharks and Rays, correspond pretty closely with 
the Cartilaginous Fishes of Cuvier. The skull is a 
simple cartilaginous box, without sutures. The 
vertebral column is more or less cartilaginous, 
and the exo-skeleton is ' placoid ' in its character 
— that is, consists of bony grains or tubercles 
scattered throughout the integument. The gills 
are peculiar, in that the branchial laminae are 
fixed like the leaves of a book to partitions which 
divide the gill-chamber into a series of pouch-hke 
spaces, which communicate internally with the 
pharynx, and externally by one or more apertures 
placed on the side of the neck, there being no 
operculum or branchiostegal rays. The structure 
of the intestine and of the heart is the same as in 
the Ganoidei. 

Sub-order (A). The Holocephali — including the 
Chimcera nionstrosa, which often accompanies 
herring shoals, hence called the ' King of the 
Herrings.' It has the mouth terminal in position, 
and only a single gill aperture on each side of the 
neck, covered by an imperfect operculum. 

Sub-order (B). The Plagiostotni, which have 
the mouth transverse, and placed on the under 
surface of the head. There are several apertures 
representing gill-slits on each side of the neck. 
It includes the Port Jackson Shark {Cestracion 
Philippi) of the Australian seas, with its curious 
pavement-like teeth, adapted for crushing the 
Crustacea and moUusca upon which it feeds. The 
Selachii, including the true Sharks and Dog- 
fishes, also belong to this group. They are dis- 
tinguished from other fishes by many peculiarities : 
in several species, the young are produced alive, 
the eggs being hatched within the body of the 
parent ; and in others, the eggs are inclosed in 
a horny casing, which has often long tendril-like 
appendages, that coil around and attach the mass 
to other bodies. This is the case with the eggs 
of the common Dog-fish and Skate of our coast, 
the receptacles being vulgarly known as * sea- 
purses.' 

The sharks are distinguished by their length- 
ened spindle-shaped bodies, by the gill-slits being 
placed laterally on each side of the neck, and by 
the fact that the pectoral fins have the ordinary 
form and position. The White Shark {Carcharias 
vulgaris) is the most celebrated species of the 
tribe, being, from its size and voracity, the terror 




White Shark {Carcharias vulgaris). 

of mariners in the seas it inhabits. It frequents 
warm latitudes, but has occasionally visited the 
British shores. It has been known to attain a 
length of thirty feet, and the opening of the jaws 
in the largest individuals is sufficient to admit 
11 



with ease the body of a man. As the mouth is 
placed in the under surface of the head, the fish 
cannot bite while in the act of swimming forwards, 
so that a dexterous person has been known to 
defend himself from its attack. The teeth are 
triangular and lancet-shaped, with acute points 
and edges, and form several rows ; they are not 
fixed in the jaw itself, but in a muscular membrane, 
by which they are erected and made to project 
when in use, lying flat in the intervals. As the 
foremost are torn away, they are replaced with 
others, which are brought up from the rows 
behind. The Blue Shark (C glaticus), which 
frequents the Mediterranean, is not unfrequently 
a source of great trouble to the fishermen of our 
coasts, on account of the injury which it does to 
their nets. It sometimes attains the length of 
eight feet. The Zygcena malleus, or Hammer- 
headed Shark, is a remarkable genus, so named 
from the projection of the head at each side in 
the form of a double-headed hammer, with an 
eye in the middle of each extremity. The Fox- 
shark (C Vulpes) is a British species. It is also 
called the Thrasher, from the use it makes of its 
tail, the upper lobe of which is elongated and very 
powerful. 

The last group, the Batides, including the Rays, 
and Skates, and Thombacks {Rata clavata), are 
remarkable for extreme horizontal flattening of the 
body, on the under surface of which, a little behind 
the mouth, the gill-slits are disposed in two rows. 
They abound rather in temperate than tropical 
seas. The eyes are placed on the back or upper 
surface. The most interesting of all is the Electric 
Ray or Torpedo of the Mediterranean. It pos- 
sesses an electrical apparatus, by which it can 
give a smart shock to any animal it touches. The 
flesh of the ray is wholesome. The skin of some 
of them is employed in the arts for polishing, and 
from that of others shagreen is made. In the 
Pristis, or Saw-fish, the body is not flattened like 
the typical rays, but bears a resemblance in its 
form and general characters to the sharks. Its 
snout is extended like the blade of a sword, with 
strong and cutting tooth-like spikes on both sides. 
This fish sometimes measures from 12 to 15 feet, 
and will attack and inflict dreadful wounds even 
on large whales. Of the Scylliidce, or Dog-fishes, 
three species are known on our coasts. They 
are distinguished from the true sharks by their 
oviparous reproduction. Their skin is used by 
cabinetmakers as a fine rasp, under the name of 
* fish-skin.' 

Order 6. Dipnoi — including only the singular 
Mud-fishes {Lepidosiren) of the Gambia and the 
Amazon. They are peculiar in that they exhibit 




Lepidosiren {Lepidosiren annectans). 

a distinct transition between the Fishes and the 
Amphibia. They inhabit marshy places, and are 
able in the dr>' season to bury themselves in the 
mud, there remaining dormant until the return of 
the rainy season. 

161 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



CLASS II.— AMPHIBIA. 

This class was included by Cuvier along with 
the Reptiles, but there is sufficient reason for 
separating them into a distinct group of equal 
importance. They may be regarded as inter- 
mediate in their structure and in their habits and 
mode of life, as well as in many of their forms, 
between Fishes and true Reptiles. To the former 
they are allied, in that at some period of their 
life they breathe by gills, but differ from them in 
always possessing lungs in the adult condition. 
Their limbs are never in the form of fins. The 
skull articulates with the vertebral column by two 
occipital condyles, and the heart consists of two 
auricles and a single ventricle. From the arterial 
and venous blood being mixed in the ventricle, 
the body is nourished by imperfectly oxygenated 
blood. They are, like Fishes and Reptiles, cold- 
blooded animals. They all undergo a metamor- 
phosis after their expulsion from the egg. At 
first, they possess gills, and are water-breathing 
animals ; but in the adult state they invariably 
possess lungs. In some genera, the gills dis- 
appear as the lungs are developed ; but in other 
cases, both gills and lungs are permanently retained 
throughout life. As in Reptiles, the gut, and the 
ducts from the kidneys and generative organs, 
open into a common cloaca. 

Order i. Ophiomorpha (serpent-forms) — in- 
cluding one genus, the Cacilia, Blind Newt, or 
Naked Serpent It is snake-like in form, and 
destitute of limbs. The eyes are exceedingly 
small, and are nearly hidden under the skin. It 
is a native of South America, Guinea, and Ceylon. 

Order 2. Urodela, or Tailed Amphibians. — 
The animals included under this group retain 
their tails in the adult condition, and their skin 
is soft, and destitute of scales. In one section 
(Amphipneusta), both gills and lungs are re- 
tained throughout life — for example, the Proteus 
of the caves of lUyria, and the Siren or Mud-eel 
of the rice-swamps of South Carolina. In the 
second section, the gills disappear at maturity, 
and the animals breathe by lungs alone. This 
section includes the Land and Water Salaman- 
ders. The Tritons, or Aquatic Salamanders, 




Warty-newt {.Triton crtstatus). 

commonly called Newts, have their tail verti- 
cally compressed, and are oviparous. They 
pass the greater part of their life in the water. 
They possess the remarkable power of repro- 
ducing limbs that have been cut off. The 

162 



anterior limbs are developed first in the Sala- 
manders, the reverse of what takes place amongst 
the frogs. Three species are indigenous to 
Great Britain. The Land Salamanders {Sala- 
mandrd) are distinguished from the former by the 
cylindrical form of their tail, and by their pro- 
ducing their young alive. AH these forms are 
easily distinguished from the Reptiles by always 
possessing gills at the earlier period of their life, 
and by the soft, smooth, naked skin. 

Order 3. The Anoura, or Tail-less Am- 
phibians, including the Frogs and Toads. The 
adult is destitute of both gills and tail, both of 
which structures exist in the larva. Four limbs 
are always present. The larvas are known as 
'tadpoles,' which have a round head, a fish-like 
tail, and breathe by gills. Ultimately, the tail 
disappears, limbs are budded forth (the posterior 
pair first), and the gills are replaced by lungs, so 
that the adult is an air-breathing animzd. 

Family RanidcB, or Frogs {rana, a frog). They 
are so well known that a description of them 
seems unnecessary. They always possess teeth 
in the upper jaw. They are of a yellowish-brown 
colour, with black spots, and their power of leaping 
is well known. As there are no movable ribs to 
expand the thorax, the mode of breathing is pecu- 
liar. The animal closes its mouth, and fills it 
with air taken in through the nostrils ; the nostrils 
are then closed, and by the compression of the 
muscles of the throat and cheeks, the air is pro- 
pelled forcibly into the lungs. The animal would 
be choked if the mouth was held open. No doubt, 
the skin also aids in the process of respiration. 
Their feet are webbed, and suited for swimming. 
Of the European species, the Edible Frog (A'. 
esculentd) is the one most approved of on the 
continent for culinary purposes. The R. tem- 
poraria is the only species indigenous to Britain. 
The Tree-frogs {HylcB) of America have their 
feet provided with suckers, which enable them to 
climb trees in pursuit of their food — insects. 

Family Pipida, distinguished by the absence of 
the tongue, including the ugly Pipa Americana, or 
Surinam Toad, which is eight inches long in the 
tadpole condition, while the perfect frog is only 
three in length. It is a native of Brazil and 
Surinam. 

Family Btifonidce (Toads) in which the jaws are 
destitute of teeth. They are of a dull, cadaverous 
appearance, and their bodies are covered with 
warts. They have a swelling above each eye, 
from which a fetid, milky secretion is expressed. 
Two species are found in Britain, the Common 
Toad {Bufo vulgaris), and the Natterjack {B. 
calamitd). They seldom frequent the water but 
for the purpose of depositing their eggs. The 
tongue in these animals, as in the frogs, is fixed 
to Xhe front of the mouth, andy)-^^ behind. 

CLASS IIL — REPTILIA. 

The Reptilia, or creeping animals {repo, I creep), 
though in outward form many of them resemble 
the Amphibia, yet in intimate structure they are 
more closely allied to birds. They are oviparous, 
and many of them are covered by hard scales, but 
never by feathers. They never breathe by gills, 
but always by lungs. The heart consists of two 
auricles and a ventricle, so that only a portion^ 
of the blood returned by the veins is propelle 



ZOOLOGY. 



through the lungs, the greater part passing again 
into the circulation without being aerated. Hence 
it is that the blood is cold, the digestive powers 
weak, and their vitality low, so that their functions 
may be suspended for a considerable time without 
apparent injury to the animal. The skull is 
articulated to the vertebral column by a single 
occipital condyle. 

Order i. Chelonia. — In typical species, the 
ribs are expanded so as to form but one bony 
plate, having no flesh outside, but being covered 
with horny plates, secreted from the skin like hair 
or nails ; the breast-bone is similarly expanded 
into a plate, covering the whole of the lower sur- 
face, and joining the edges of the upper plate ; so 
that the animal may be said to be sheltered in a 
box formed of its bones. Within this box, the 
upper plate of which is named the carapace, and 
the lower the plastron, the animal can even with- 
draw its head and feet, and thus set most enemies 
at defiance. There are no teeth, and the edges of 
the jaws are sheathed in horn, so as to form a 
kind of beak. 

The family Chelonidce (Turtles) are designed 
for sea-life, and their extremities take the form of 
paddles. They swim with great ease, and only 
come to land to deposit their eggs, which they 
do thrice a year, laying about loo at a time. They 
feed chiefly on marine plants. They are sometimes 
five feet in length, and weigh 800 pounds. The 
Chelone midas (Edible or Green Turtle) of the 
tropical seas of America, is noted for the delicious 
food which it yields. Ascension Island is one of 
their favourite retreats. 

The Chelone imbricata (Hawk's-bill Turtle) is a 




I, Hawk's-bill Turtle (Chelone imbricata) ; 2, Green 
Turtle {Chelone midas). 

smaller species, and is remarkable for the imbri- 
cate beautifully marked horny plates covering its 
carapace, which yields the tortoise-shell of com- 
merce. These plates do not join at the edges like 
those of land-tortoises, but overlap each other like 
the scales of other reptiles. The finest tortoise- 
shell is brought from the Indian Archipelago. 

The Chelone or Sphargis caretta (Leathery 
Turtle) has the carapace covered by a leathery 
skin in place of homy plates. This animal in- 



habits the Mediterranean as well as the Atlantic 
and Pacific Oceans. 

The family of the Etnydce (Terrapenes) and the 
TrionycidcB (Mud Turtles) have the feet furnished 
with toes, and being partly webbed, they are useful 
for swimming. The Snapping Turtle {Trionyx 
ferox) of America is capable of biting through a 
stick half an inch in diameter. The T. Niloticus is 
highly serviceable in the Nile and other rivers in 
destroying young crocodiles and alligators. They 
are all inhabitants of fresh water. 

The TestudinidcB (Land Tortoises) have the feet 
furnished with short nails, and adapted for walking 
on firm ground. Their armour is thicker and 




Common Land Tortoise {Testuda graca). 

stronger in proportion to their size than the aquatic 
species. They are vegetable feeders. The T. 
grceca of Spain is often kept as a domestic pet 

Order 2. Ophidia — have an elongated cylin- 
drical body, covered with scales, but destitute 
of limbs, though in some serpents rudimentary 
posterior limbs can be traced, but these are of 
no use for progression. The ribs are exceedingly 
numerous, and very movable, and their pointed 
extremities are attached by muscles to the ab- 
dominal scales, or 'scuta,' of the integument. 
By this arrangement, the animal moves along on 
the points of its ribs, the whole being facilitated 
by the very movable spinal column. The tongue 
is forked, and there is no eyelid, the eye being 
covered with a glassy capsule, within which the 
eye moves freely. All are furnished with teeth, 
which never occupy distinct sockets, but are 
united to the jaw, and are arranged either in two 
or three rows. The two halves of the lower jaw, 
which are composed of several pieces, are united 
in front by ligaments and muscles, which permits 
of their being separated to a considerable distance, 
so that, though the head is small, these animals 
are enabled to swallow their prey entire. They 
remain torpid during winter, and each season cast 
their skin. 

Sub-order i. Viperina, or Venomous Snakes — 
have a pair of perforated poison-fangs in the 
upper jaw, which can be erected or depressed at 
will. When the animal is irritated, they are un- 
folded, and struck into the victim, the poison 
being at the same time ejected by the action of the 
muscles of the jaws. The matter is poisonous only 
when introduced into the blood. The Viperina 
comprise the Rattlesnakes {Crotalidce) of America, 
which are distinguished by a pit behind each 
nostril, and by the presence of the rattle. They 
are highly venomous, but they will not attack man 
unless when trodden on or provoked. The ex- 
tremity of the tail in Crotalus horridus is furnished 

I ^ 163 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



with a series of homy epidermic rings, known 
as the ' rattle,' which produces a rattling noise 
when the animal moves, hence the name. Some 




Common Viper, or Adder {Polios berus). 

measure five or six feet in length, and are as 
thick as a man's arm. Their food consists of 
birds and small animals. The Viperine Snakes 
are distinguished from the former by a broader 
head, by the absence of the rattle, as well as the 
cavities behind their nostrils. They are entirely 
confined to the Old World, in the warm countries 
of which they are very abundant. The Common 
W^r {Pelias bents) can inflict a dangerous bite, 
and is the only venomous reptile found in Britain. 

Sub-or(Ur 2. The Colubritia — in which the 
maxillary bones are armed with solid conical 
teeth. If fangs are present, they are only grooved 
on one side. They are for the most part harm- 
less, but some of them are extremely venomous. 
This sub-order may be divided into two sub- 
orders : 

(a.) Innocua, or Harmless Snakes, in which 
there are only solid teeth on the maxillse. The 
Coluber natrix (Ringed Snake) of Britain, and the 
C. constrida (Black Snake) of North America, 
are perfectly harmless. The former is tolerably 
abundant in Britain, and is a very pretty little 
creature, about three feet in length. It is of a pale 
olive colour, spotted in black on the sides, and 
immediately behind there is on each side a 
yellowish spot, which gives to the animal its 
common name of Ringed Snake. 

The Boa Constrictors of tropical America have 
the under part of the body and tail covered with 
transverse shields. Many of the species exceed 
twenty feet in length, and they can swallow even 
sheep and oxen. This they effect by coiling them- 
selves round the body of the victim, and crushing 
it till every bone is broken. They then moisten 
it with saliva, and proceed to swallow it. The 
Pythons are inhabitants of the Old World, and 
many of them, from their size and great muscular 
power, are amongst the most formidable of all 
Ophidia. 

(^.) In the group Venenosa, which have grooved 
fangs placed in front of the upper jaw, and solid 
teeth behind them, are included some of the most 
venomous of all snakes. The most formidable of 
these is the Hooded Snake, Cobra di Capello 
{Naja tripudians) of India, the snake usually 
carried about by the Indian snake-charmers, the 
bite of which i? fatal within an hour. The Hydro- 
phidcB (Water-serpents) have a vertically com- 
pressed tail, and so can swim with great facility. 

164 



They are very venomous, and are chiefly found in 
the rivers and seas of the East Indies. 




Cobra di Capello {Naja tripudians). 

Order 3. The Lacertilia — comprising the 
Lizards, which have a lengthened body, terminat- 
ing in a tail, and covered with small scales. 
Eyelids are present in all with the exception of 
the Geckotidce. As a general rule, four limbs are 
present, although the Blind-worm or Slow-worm 
{Ang7ds fragilis), -which, belongs to the family of 
the ScincidcE, has no external appearance of limbs, 
although the bones of the pelvis and shoulder 
exist in a rudimentary condition under the skin. 
It is serpentiform, and quite harmless, and when 
alarmed, its muscles become so rigid that the tail 
can be broken off. In the course of a year, how- 
ever, this member is replaced. It is found all 
over Europe, and feeds upon insects, slugs, &c. 
Nearly allied to the former are the ArnphisbcEnidce 
(Double-walkers). They can move forwards or 
backwards with equal facility. They are small 
harmless animals, found in the warmest parts of 
South America. These serpentiform Lacertilia 
are at once distinguished from the Ophidia by the 
structure of the lower jaw, the two halves of which 
are united in front by a suture so as to restrict 
the gape. 

In order that any one may be able readily to 
make out the differences between the three snakes 
indigenous to Great Britain, and thus perhaps be 
saved from the danger that might accrue from 
handling or incautiously approaching a viper, mis- 
taking it for the harmless ring-snake or coronella, 
we give an illustration and brief description of the 
heads of the three species. 

I. The common ringed snake has a somewhat 
almond-shaped head, covered with broad plates or 
shields. It has invariably a yellow collar at the 
back of the head, the yellow colour being made 
more apparent by a jet-black collar behind it. 
This black collar does not in every case extend 
right across the neck, but varies in different speci- 
mens. The eye is rather prominent, of a hazel 
colour. The prevailing colour of the back and 
sides is dusky brown. The centre line of the back 
is marked with a double row of small black spots, 
which extend from the head to the tail, and from 
these rows, lines made up of similar dots stripe the 
sides. 



ZOOLOGY. 



2. The head of Coronella l^vis, it will be at 
cnce evident, is exceedingly small, compared with 






i, The Common Ringed Snake [Coluber natrix) ; 2, The 
Small-crowned Smooth Snake ( Coronella Iczvis) ; 3, 
The Common Viper or Adder (Felias berus). 

the other two ; moreover, it is rounder, and more 
like the head of a lizard, and carried in a more 
erect position than the head of the ring-snake. 
The plating on the top of the head is very like that 
of the ring-snake, but the lateral plates differ from 
those of the viper. One marked peculiarity in the 
head of Coronella IcEvis is that it is beautifully 
iridescent, and of bronze green colour. There is 
but a very imperfect V-mark — not at all distinct, 
like the brand on the viper, being broken or im- 
perfect at the sharp terminal angles, while that on 
the viper is complete. The general colour of the 
skin is brown ; and it is remarkable for its almost 
polished smoothness, which gives the reptile its 
name, IcEvis. Two rows of dark spots run along 
the sides of the back, which at once distinguish it 
from the viper, with its zigzag marking. The belly 
is a brightish orange colour. 

3. The head of the viper, it will be observed, is 
not shaped like the head of the snake ; it is per- 
fectly flat. The viper has no collar encircling the 
neck, but instead the letter V distinctly marked on 
the back part of the head, as will be more plainly 
seen by reversing the illustration. It really would 
almost appear that nature had branded this, the 
only poisonous reptile inhabiting our land, so that 
people might the more easily recognise and avoid 
it, with V, the first letter in the name viper. Con- 
tinuing from this V-marking, a diamond-shaped 
f)attern of a dark colour extends along the whole 
ine of the back. The general colour of the body 
is extremely variable, being influenced by local 
conditions. 

With respect to its dangerous properties, Mr 
Bell remarks : 'In this country, I have never seen 
a case which terminated in death, nor have I been 
able to trace to an authentic source any of the 
numerous reports of such a termination. At the 
same time, the symptoms are frequently so threat- 
ening, that I cannot but conclude that in very hot 
weather, and when not only the reptile is in full 
activity and power, but the constitution of the 
victim in a state of great irritability and diminished 
power, a bite from the common viper would very 
probably prove fatal. The poisonous fluid is per- 
fectly innocuous when swallowed. Dr Mead and 
others have made this experiment, and never ex- 



perienced the slightest ill effects from it It is, 
however, clear that there would be danger in 
swallowing it were any part of the mouth, the 
throat, or the oesophagus in a state of ulceration, 
or having an abraded surface.' 

The family of the LacertidcB (Lizards) have 
four limbs, terminated by five toes of unequal 
lengths. Their tongues are long, slender, and 
protrusile. Their bodies are covered with scales, 
and the head and abdomen with large regular 
plates or ' scuta.' They are terrestrial in their 
habits, as their rounded tail indicates. They vary 
from five to thirty inches in length. They feed 
upon frogs, insects, and small mammals. The 
Scaly Lizard {Zootoca vivipard), which is vivipar- 
ous, whence its specific name, is found abundantly 
in this country on dry banks and sandy heaths, 
where it may be observed basking in the sunshine, 
watching for its insect prey. The Lacerta agilis 




I, Viviparous Lizard [Zootoca vivipara) ; 2, Sand Lizard 

(Lacerta agilis). 

(Sand Lizard) is found in England, and the L. 
viridis (Green Lizard) is common in Jersey. 

The Varanidce (Monitors) are closely allied to 
the former, but differ from them in having the 
head and abdomen covered with ordinary scales. 
They sometimes measure six feet in length — for 
example, the Varanus Nilotus of Egypt. They 
are also called Monitors, because they warn each 
other of the approach of an enemy by a shrill 
whistling sound. They are confined to the Old 
World. 

Family Iguanidce (Iguana, or Guana Lizards) 
are distinguished from the true lizards by a 
short and thick tongue, with the extremity very 
slightly cleft. It contains several genera. Iguanas, 
properly so called, are covered with small scales, 
and they have a dorsal crest and a compressed 
tail, and are confined to the New World. A large 
thin fold of skin, or dewlap, hangs from under the 
throat. Each jaw has a range of triangular teeth, 
with finely sharpened edges, and a double row 
also on the palate. They feed upon vegetable 
substances, and live chiefly upon trees. They 
sometimes measure four feet in length ; and both 
their flesh and eggs are esteemed as delicacies. 
One of the most remarkable American species 
is the Basilisk {Basiliscus Ameficanus), which, 
although perfectly harmless, is one of the most 
forbidding of reptiles. It is distinguished by a 
mitre-shaped crest on the top of its head. The 



CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Amblyrynchiis cri status of the Galapagos Isles, 
first described by Mr Dar\vin, is partially aquatic 
in its habits, spending the greater part of its time 
in the sea. 

A gigantic fossil form, the Iguanodon, charac- 
teristic of the Wealden Period, had teeth closely 
resembling the Iguana of the present day. It 




Flying Lizard {Draco volam). 

attained the length of fifty feet More remarkable 
than the iguanas is the Flying Lizard {Draco 
volans) of the East Indies. It is a small animal, 
possessing a membrane at its sides, stretched 
over the false ribs, by which it can float, though 
it has no true power of flight, as upon a parachute, 
from one tree to another. 

The Geckotida, or Nocturnal Lizards, have the 
toes terminating in little suckers, enabling the 
animal to creep up vertical walls, and along 
ceilings, like the flies upon which it feeds. They 
have a flattened body and a broad head, which, 
aided by their sombre colour, gives them a dis- 
agreeable appearance. They are timid and harm- 
less, and are common in the warm climates of the 
Old and New World. Like the Iguanidce, they 
constitute an exceedingly numerous family. 

Family Chatnaleonida (Chameleons), which 
includes the Common Chameleon (C Africanus), 
are animals of small size, with a prehensile tail. 
They are readily distinguished from other lizards 
by having climbing feet, and by the fact that the 
eye is covered by a circular hd, which is perforated 
by a small opening opposite the pupil. They are 
natives of the Old World, and live in trees, 




Chameleon {Camceleo Africanus). 

which they seldom leave. Their prey, consisting 
of flies and insects, is taken by darting out the 
glutinous tongue, which is terminated by an 

166 



adhesive disk. They are also remarkable for the 
power they possess of changing their colour. 

Order 4. Crocodilia (Crocodiles) — are inhabit- 
ants of the rivers and fresh waters of equatorial 
countries. They are formidable animals, and 
attain the length of twenty or thirty feet. The 
head is large, and each of the lengthened jaws is 
furnished with a single row of teeth, which are 
implanted in distinct sockets. The back and tail 
are covered with strong dermal plates, per- 
mitting of easy motion of the body and limbs. 
The back is impenetrable to a musket-ball. On 
land, the motion of the animal is slow, because 
the legs are short, and the feet are palmated ; but 
in water it moves rapidly, using the tail as a 
powerful oar. The tail, with its serrated ridge of 
scales, is a formidable weapon of oflence and 
defence. These animals usually feed upon decayed 
carcasses that may come in their way, and are 
thus of considerable sei-vice in the hot countries 
which they inhabit. The eggs, which are about 
the size of those of a goose, are deposited in the 
sand, and hatched by the sun. There is only a 
single genus in this order containing three species 
— I. The true Crocodile, which abounds in the 




Gavial (Gauialis Gangetkus). 

Nile ; 2. The Alligator, found in the rivers and 
swamps of North and South America; and 3. 
The Gavial, which inhabits India and the islands 
of the Eastern Archipelago. 

Fossil Reptiles. — The Ichthyosaurus, from the 
Lias and Oolite strata, was a marine animal, some- 
times twenty feet long, possessing the vertebras of 
a fish, with paddle-feet, like those of a turtle, and 
a crocodile-like head, armed with sharp and 
formidable teeth. The Plesiosaur was a smaller 
animal, with a neck of extraordinary length, and 
a small head. But the most singular fossil saurian 
is the Pterodactyle, which had the last digit of 
the fore-limb extraordinarily lengthened. It was 
furnished with a pair of wings, like those of a bat, 
and thus is supposed to have been able to fly 
through the air in pursuit of its prey. 

CLASS IV.— AVES, OR BIRDS. 

These are oviparous vertebrates, with a complete 
double system of circulation, with its proper con- 
sequence of warm blood. The skull is articulated 



ZOOLOGY. 



b 



to the vertebral column by a single occipital con- 
dyle. The young are hatched and nurtured by 
the parent. Their body is covered with feathers, 
instead of hair or wool ; and, as a rule, the fore- 
limbs are in the form of wings adapted for flight, 
but they are never used for prehension. The 
lungs are fixed in the chest, and the air-tubes 
open on the surface of the lungs into air-cells, 
scattered throughout the body. By this organisa- 
tion, they can increase or diminish their density, so 
as to range over the aerial regions with ease and 
celerity. The bones of birds are singularly light, 
and exhibit a greater degree of hardness than in 
any other vertebrate. The lightness is due to the 
marrow being replaced by air, and the hardness 
to the presence of a large proportion of phosphate 
of lime. The eye is generally so constructed that 
they can see objects far and near with almost 
equal clearness. Their posterior extremities serve 
as the sole support of the body on the ground. 
Most commonly the feet exhibit four toes, of 
which one is directed behind, and three in front. 
In the single posterior toe, the number of joints is 
two ; in the external, five. The toes are terminated 
by claws, which are used for different purposes. 
Birds have no teeth, and therefore cannot masti- 
cate their food, which is either torn by the beak 
or swallowed whole, and is reduced to a soft state 
in the stomach. The plan of the digestive system 
most usual in this class is that which is exempli- 
fied in the common fowl. The stomach consists 
of three cavities : the first being formed by an 
expansion of the gullet, which produces a bag or 
chamber known as the crop. In this receptacle 
the food is stored up, and transferred by degrees 
to the second or membranous stomach, where it 
is softened by the action of the gastric juice. It 
is then conducted to the gizzard, or third cavity, 
in which the process of digestion is completed. 
This last stomach presents modifications varying 
with the nature of the food upon which the bird 
subsists. If it feeds on grain, the sides of this 
stomach are of considerable thickness, and are 
moved by powerful muscles, which act as a mill 
in grinding down the food ; but in those species 
which subsist on animal substances, or soft herb- 
age, the muscles are reduced to extreme delicacy. 
In many cases the process of digestion is pro- 
moted by the swallowing of small pebbles, which, 
being brought into contact with the food in the 
gizzard by the muscular action of the stomach, 
produce an effect similar to that of teeth, and in 
some measure serve the purpose of these agents. 

The change of the plumage, termed moulting, 
generally takes place annually ; while with some 
species a partial casting of the feathers occurs 
also at the breeding season. Many birds migrate 
from one latitude to another, chiefly for the sake 
of obtaining a better supply of food. The summer 
immigrants that visit our island, as the swallow, 
the rail, the cuckoo, are from tropical regions ; 
while all winter visitants, as the Swan and Wild 
Goose, come from the north. Under the direc- 
tion of their highly developed instinctive powers, 
the place